FINAL DRAFT
ECAOCIN-D008
United States Crmtomfeer
Environmental Protection oujuwinoei,
Agency
Research and
Development
DRINKING WATER CRITERIA DOCUMENT FOR
MANGANESE
Prepared for
Office of Water
Prepared by
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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DISCLAIMER
This report is an external draft for review purposes oniy and does not constitute
Agency policy. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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FOREWORD
Section 1412 (b) (3) (A) of the Safe Drinking Water Act, as amended in 1986,
requires the Administrator of the Environmental Protection Agency to publish maximum
contaminant level goals (MCLGs) and promulgate National Primary Drinking Water
Regulations for each contaminant, which, in the judgement of the Administrator, may
have an adverse effect on public health and which is known or anticipated to occur in
public water systems. The MCLG is nonenforceable and is set at a level at which no
known or anticipated adverse health effects in humans occur and which allows for an
adequate margin of safety. Factors considered in setting the MCLG include health
effects data and sources of exposure other than drinking water.
This document provides the health effects basis to be considered in establishing
the MCLG. To achieve this objective, data on pharmacokinetics, human exposure, acute
and chronic toxicity to animals and humans, epidemiology and mechanisms of toxicity
are evaluated. Specific emphasis is placed on literature'data providing dose-response
information. Thus, while the literature search and evaluation performed in support of this
document has been comprehensive, only the reports considered most pertinent in the
derivation of the MCLG are cited in the document. The comprehensive literature data
base in support of this document includes information published up to 1992; however,
more recent data m^y have been added during the review process.
When adequate health effects data exist, Health Advisory values for less than
lifetime exposures (1-day, 10-day and longer-term, -10% of an individual's lifetime) are
included in this document. These values are not used in setting the MCLG, but serve
as informal guidance to municipalities and other organizations when emergency spills or
contamination situations occur.
This document was prepared for the Office of Water by the Office of Health and
Environmental Assessment (Environmental Criteria and Assessment Office, Cincinnati,
O?"io) to provide the scientific support for the human health-based risk assessment used
in the determination of the drinking water MCLG. For more information, contact the
Human Risk Assessment Branch of the Office of Water at (202)260-7571.
Tudor Davies .
D'-ecicr
O";ce of Science and Technology
James R E icier
Director
Off ice of Ground Water and Drinking
Water
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DOCUMENT DEVELOPMENT
Susan Velazquez, Document Manager
Environmental Criteria and Assessment Office, Cincinnati
U.S. Environmental Protection Agency
Editorial Reviewer
Erma Durden, B.A.
Environmental Criteria and Assessment
Office
U.S. Environmental Protection Agency
Cincinnati, OH
Scientific Reviewers
Julie T. Du, Ph.D.
Office of Water
Washington, DC
Bemald Weiss, Ph.D.
Division of Toxicology
University of Rochester Medical Center
Rochester, NY
Ellen Silbergeld, Ph.D
Environmental Defense Fund
Washington, DC
Sheila Rosenthal, Ph.D
Vincent J. Cogliano, Ph.D
Human Health Assessment Group
Washington, DC
Richard Walentowicz, Ph.D
Exposure Assessment Group
Washington, DC
Zoltan Annau, Ph.D
Reproductive Effects Assessment Group
Washington, DC
Chon Shoaf, Ph.D
Environmental Criteria and Assessment Office
Research Triangle Park, NC
Document Preparation
Technical Support Services Staff, Environmental Criteria and Assessment Office,
Cincinnati
IV
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TABLE OF CONTENTS
Page
I. SUMMARY 1-1
II. PHYSICAL AND CHEMICAL PROPTERTIES 11-1
INTRODUCTION 11-1
MANGANESE (I) COMPOUND II-3
Methylcyclopentadienyl Manganese Tricarbonyl II-3
Manganese (II) Compounds II-3
Manganous Carbonate II-3
Manganous Chloride II-3
Manganese Ethylenebisdithiocarbamate M-6
Manganous Acetate II-6
Manganous Oxide II-6
Manganous Phosphate II-6
Manganous Sulfate II-7
Manganous Soaps II-7
MANGANESE (IV) COMPOUNDS II-8
Manganese Dioxide II-8
MANGANESE (VII) COMPOUNDS II-8
Potassium Permanganate II-8
SUMMARY II-9
III. TOXICOKINETICS 111-1
ABSORPTION 111-1
Gastrointestinal Ill-l
Respiratory 111-6
DISTRIBUTION 111-6
METABOLISM 111-12
EXCRETION 111-13
HOMEOSTASIS 111-17
SUMMARY 111-17
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TABLE OF CONTENTS (cont.)
Page
IV. HUMAN EXPOSURE IV-1
(To be provided by the Office of Water)
V HEALTH EFFECTS IN ANIMALS V-1
GENERAL TOXICITY V-1
Acute Toxicity V-1
Subchronic and Chronic Toxicity V-3
Oral Exposure V-6
Parenteral Exposure V-24
Inhalation Exposure V-27
OTHER EFFECTS V-28
Carcinogenicity V-28
Mutagenicity V-34
Reproductive Effects V-37
Teratogenicity V-38
SUMMARY V-41
VI. HEALTH EFFECTS IN HUMANS VI-1
INTRODUCTION VI-1
CLINICAL CASE STUDIES VI-1
EPIDEMIOLOGIC STUDIES VI-7
Carcinogenicity VI-* 6
Mutagenicity and Teratoce".ic.ty VM7
SUMMARY . . . VI •<"
MEGHAN'SUS OF TOXICTY \": '
MECHANISMS OF NEUROTOXICITY .. . V'.l-1
MECHANISMS OF OTHER EFFECTS VII--;
SUMMARY VII-4
V)
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TABLE OF CONTENTS (cont.)
Page
VIII. QUANTIFICATION OF TOXICOLOGIC EFFECTS VIII-1
INTRODUCTION VIII-1
NONCARCINOGENIC EFFECTS OF MANGANESE IN THE DIET VIII-7
QUANTIFICATION OF NONCARCINOGENIC EFFECTS FOR
MANGANESE IN DRINKING WATER Vlll-19
Derivation of 1-Day and 10-Day HAs Vlll-19
Derivation of Longer-term HA VIII-20
Assessment of Lifetime Exposure and Derivation of a
DWEL VIII-21
WEIGHT-OF-EVIDENCE FOR CARCINOGENIC EFFECTS VIII-21
EXISTING GUIDELINES, RECOMMENDATIONS AND STANDARDS .... VIII-24
SPECIAL GROUPS AT RISK VIII-25
IX. REFERENCES IX-1
VII
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LIST OF TABLES
No. Title Page
11-1 Estimated U.S. Production, Capacity and Use of
Selected Manganese Compounds II-2
II-2 Physical Properties of Some Manganese Compounds II-4
V-1 Oral LDjo Values for Manganese Compounds V-2
V-2 Parental LDX Values for Manganese Compounds V-4
V-3 Neurotoxic Effects of Manganese in Experimental Animals:
Oral and Inhalation Studies V-16
V-4 Neurotoxic Effects of Manganese in Experimental Animals:
Parenteral Studies V-17
V-5 Liver Effects of Manganese Exposure in Animals V-20
V-6 Summary of Carcinogenicity Studies Reporting Positive
Findings for Selected Manganese Compounds V-31
V-7 Pulmonary Tumors in Strain A Mice Treated with
Manganese Sulfate V-33
V-8 Carcinogenicity of Manganese Powder, Manganese Dioxide,
and Manganese Acetylacetonate in F344 Rats and Swiss
Albino Mice V-35
V-9 Reproductive Effects of Exposure to Manganese V-39
V!-1 Studies of Manganism in Humans and Exposure-Response
Relationship VI-2
Vi-^ Fe.rroailoy Workers with Neurologic Sigrs by Level of
Exposure to Mangarese . VI-"-
VIII-' Oral Studies on Manganese Neurotoxicity for
Quantification of Toxicologic Effects VIII-15
VIII
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LIST OF ABBREVIATIONS
CMS Central nervous system
DWEL Drinking water equivalent level
Gl Gastrointestinal
HA Health Advisory
i.m. Intramuscular
i.t. Intratracheal
i.v. Intravenous
LC50 Concentration lethal to 50% of recipients
LDjQ Dose lethal to 50% of recipients
LOAEL Lowest-observed-adverse-effect-level
MAO Monoamine oxidase
NOAEL No-observed-adverse-effect level
RfD Reference dose
RSC Relative source contribution
s.c. Subcutaneous
IX
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!. SUMMARY
Manganese is a gray-pink metal that is too brittle to be used unless alloyed. It
exists in 11 oxidation states with the compounds containing Mn , Mn and Mn +
being the most economically and environmentally important.
Manganese is absorbed from the G! tract after i.ngestion and is distributed
primarily to the liver, kidney, endocrine glands and brain. The absorption of manganese
is low, averaging 3-9% in adults. Bile is the main route of excretion of manganese and
represents the principal regulatory mechanism. The metabolism of manganese is
controlled by homeostatic mechanisms at the level of excretion as well as absorption,
which respond very efficiently to increases in manganese concentration. However,
prolonged exposure to excess manganese lessens the efficiency of the homeostatic
mechanism. The biologic half-life ranges from 2-5 weeks and depends upon body stores
of manganese. In both humans and animals, the biologic half-life decreases with
increased exposure. Retention in the brain appears to be longer than in other parts of
the body
Manganese .s an essential element, being required by mammals and birds for
.':o;r normal growth and rna.ntenance of health. However, manganese deficiency is
;;racticaily nonexistent in humans as it is widely available in the diet. Manganese is also
considered to be of low toxicity because of efficient homeostatic controls that regulate
tne absorption and excretion of manganese. However, high levels of manganese can
result m poisoning, particularly by the inhalation route of exposure.
MANGANES! 1-1 01/05/93
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The CMS is the primary system affected by chronic exposure to high levels of
manganese. The human neurobehavioral deficits (e.g., tremor, gait disorders) resulting
from manganese poisoning can be reproduced in other primates but not in rodents.
Parenteral administration of manganese to monkeys results in extrapyramidal symptoms
and histologic lesions in the brain, which resemble those seen in human manganism.
However, by the oral route there has been only one limited study using primates that
employed only one dose level. Studies of rodents orally exposed to manganese report
neurochemical, but not behavioral effects as seen in humans. Therefore, these studies
are of questionable relevance with respect to human health risk assessment.
In chronic manganese toxicity, several neurotransmitter systems in the brain
appear to be affected. The primary effect is on the levels of monoamines, especially
dopamine, but the precise mechanism of this effect is not understood.
Studies on occupationally exposed humans, although supporting the association
of neurotoxic effects with inhalation exposure to manganese, have not provided a clear
dose-response relationship. Most human studies have related to inhalation exposure
and have found that exposure to levels > 5 mg/m3 have been associated with neurotoxic
effects.
A Japanese study of health effects resulting from the ingestion of manganese-
contaminated drinking water for several months found neurotoxic signs and symptoms
occurring at drinking water concentrations estimated to be roughly 28 mg Mn/L In
contrast to what has been shown in laboratory animals, children were less affected than
MANGANES.I 1-2 02/23/93
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adults by this exposure. The elderly were most severely affected. An epidemiologic
study performed in Greece has shown that a lifetime consumption of drinking water
containing naturally high levels of manganese (up to 2 mg/L) leads to increased
manganese retention as demonstrated by the concentration of manganese in hair. At
levels of about 2 mg/L, the authors suggested that some neurologic impairment may be
apparent in people over 50 years of age. These two studies provide the basis for the
establishment of separate risk assessments for manganese in food and water.
There are no epidemiologic studies investigating the relationship between
manganese exposure and carcinogenic, mutagenic or teratogenic effects in humans.
The National Toxicology Program (NTP, 1992) conducted a 2-year feeding
bioassay of manganese sulfate in B6C3F1 mice and F344 rats. No evidence of
carcinogenicity was seen in mice. In rats there was equivocal evidence based on an
increased incidence of thyroid follicular cell tumors, but only at very high doses of
manganese. The relevance of these tumors to human carcinogenesis is questionable.
Existing guidelines recommend a maximum concentration of 0.05 mg/L for
manganese in freshwater to prevent undesirable taste and discoloration. For the
protection of consumers of marine mollusks, a criterion for manganese of 0.1 mg/L for
marine waters has been recommended. The rationale for this criterion has not been
specified, but it is partially based on the observation that manganese can bioaccumulate
in marine mollusks.
MANGANES.I I-3 02/23/93
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There are insufficient data to calculate separate 1-day and 10-day HAs for
manganese in drinking water. The HA values of 1 mg/L are based on the RfD for
manganese in water. Shorter-term exposure to higher levels of manganese is generally
not of great concern because of the efficient homeostatic mechanisms in manganese
metabolism and the taste and odor properties of manganese.
While there are limited data on the toxicity of ingested manganese in humans,
there are several studies demonstrating levels of manganese in the diet that are safe and
adequate for chronic human consumption. An RfD (food) of 0.14 mg Mn/kg/day
(verified by the RfD/RfC Wonxgroup in June 1990) has been calculated based on these
safe and adequate levels. It is also noted that some diets, particularly vegetarian diets,
may contain higher levels of manganese. While the intake of manganese from these
diets may exceed the RfD (equivalent to 10 mg Mn/day), the bioavailability of
manganese from vegetable sources is substantially decreased by dietary components
such as fiber and phytates. Therefore, these intakes are considered to be safe as well.
It is emphasized that this RfD was calculated for total dietary manganese, which under
normal circumstances accounts for virtually all manganese intake.
Trie two studies of humans ingesting significant quantities o* manganese :r,
d'.r.Mpg water led to the development of a separate drink ng water RfD In Sec'.emce-
1992. the RfD/RfC Workgroup verified a drinking water RfD of 0.005 mg kg/day
Assuming a body weight of 70 kg and a drinking water consumption of 2 L day this is
roughly equivalent to water concentration of 200 Mg Mn/L. Because the stud'es used
to support the drinking water RfD assumed that there was an additional dietary
MANGANES.I I-4 01,05/93
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contribution of manganese, the RfD assumes the same. Therefore, no relative source
contribution needs to be factored in and the concentration of 200 ng Mn/L may be used
directly in the setting of drinking water standards.
MANGANES.I 1-5 01/05/93
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II. PHYSICAL AND CHEMICAL PROPERTIES
Introduction
Manganese is a brittle, gray-pink metal with an atomic weight of 54.938. It is too
brittle to be used unless alloyed. The CAS registry number is 7439-96-5. Manganese
has only one stable natural isotope, 55Mn. Its melting point is 1244°C and the boiling
point is 1962°C. It can exist in 11 oxidation states, with valences of 2 + , 4+ and 7 +
being the most common. The four allotropic forms of manganese are alpha, beta,
gamma and delta, with the alpha form being stable below 710°C. The gamma form
decomposes to alpha at normal temperatures. Manganese has a density of 7.43 at
20°C and a vapor pressure of 1 mm Hg at 1292°C. Pure electrolytic manganese is not
hydrolyzed at normal temperatures. It does decompose slowly in cold water and more
rapidly when heated.
The principal use of manganese is in the manufacture of iron, steel and other
alloys, which accounts for about 95% of the U.S. demand. A minor use of manganese
is in pyrotechnics and fireworks. Manganese compounds are used as feed additives
and fertilizers, colorants in brick and tile manufacture, components in dry cell battery
manufacture, precursors in chemical manufacture and processing, and fuel additives
(US EPA, 1984). Table 11-1 gives estimated production capacities for several
;nanganese compounds.
The manganese compounds most economically and environmentally important
are those that contain Mn2', Mn4* and Mn7 + . The 2+ compounds are stable in acid
solution but are readily oxidized in alkaline medium. The most important Mn4 * compound
MANGANES.II 11-1 02/11/93
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TABLE 11-1
Ettiavted U.S. Production, Cecity end Use of Selected Manganese Compounds*
Product Formula
Electrolytic manganese MnO,
Nigh purity manganese oxide MnO
601 manganese oxide MnO
Manganese sulfate MnSO,
Mengancse chloride MnCl,
Potass fun permanganate KMnO,
Methyl eye lopentadieny I manganese CH.C.H.MnfCO},
tricarbonyl (MMT)
•Source: Adapted from Reidies, 1981
EttlHttd U.S. Production
Capacity (Mtric tons/year
18,000
9.000
36,000
68,000
3.000
u.ooo
500-1,000
Dry-cell batteries; ferrittt
Nigh-quality ferrites; ceramics; Irtenaedlate for high purity
Hn (II) salts
Fertilizer; feed additive, intertwdiate for electrolytic
•anganese ewtal and dioxide
Feed additive; fertilizer; intermediate for awty products
Metallurgy. MHT synthesis; brick colorant; dye; dry-cell
batteries
Oxidant; catalyst; intermediate; water and air purifier
Fuel additive
MANGANES.II
1-2
12/07/92
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is the oxide, MnO2, also known as pyrolusite. Manganese colors glass an amethyst
color and is responsible for the color of true amethyst (U.S. EPA, 1984). Several
important compounds of manganese are described in the following text and in Table II-2.
Manganese (I) Compound
Methylcyclopentadienyl Manganese Tricarbonyl. CH3C5H4Mn(CO)3 or MMT
is a light amber liquid that is added to fuels to prevent engine knock and as a smoke
suppressant. It has a specific gravity of 1.39 at 20°C and is insoluble in water (U.S.
EPA, 1984).
Manganese (II) Compounds
Manganous Carbonate. MnCO3 is a naturally-occurring compound, but it is
produced commercially by precipitating it out of manganese sulfate solutions. It is used
in the production of ferrite, animal feeds, ceramics and as a source of acid soluble
manganese (U.S. EPA, 1984). MnCO3 is a rose-colored rhombic compound that turns
light brown when exposed to air. It has a density of 3.125 at 20°C. It is soluble in water
and dilute acid.
Manganous Chloride. MnCI2 can exist in both the anhydrous form and as a
rv/drate with 6, 4 or 2 water molecules. The anhydrous form is a pink, cubic crystalline
structure, also known as scacchite. It has a density of 2.977 at 25^C. The hydrate form
(•4H2O) is a rose colored monoclinic crystalline structure. It has a density of 2.01 at
MANGANES.II II-3 02/16/93
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TABLE 11 -2
Physical Properties of Sow Manganese Compounds'
NMM and CAS Vati
Registry Nunfcer
mce Chemical Holacular Specific
Formula Weight or Dei
•
Hethylcyclopentadteoyl «1 CH.C.H.HntCO), 218.09 1.39
Manganese tricarbonyl
(MMT) (12108-13-31
Manganous carbonate* »2 MnCO, 114.95 3.12S
[598-62-9]
Manganous chloride »2 MnCl, 125.84 MS
(7773-27-01-5)
Manganous acetate »2 Mn(C,H,0,><*4H,0 245.06 1.589
(15243-27-3)
Manganous acetate »2 Mn(C,H,0,), 173.02 1.74
C638-S8-0]
Manganese «2 CH,MHCS,),Mn 265.24 MS
ethylenebisdithiocarbamate
(Naneb) (12427-38-2)
Gravity Netting lottf
rwity Point (*C) Point
1 1
1.5 233
decoapoae* NS
650 1190
NS NS
NS NS
NS NS
Manganous oxide *2 HnO 70.94 5.43-5.46 1945 NS
(1344-43-0)
Manganou* phosphate (NS] *2 Mn,(PO.)t 259.78 MS
Manganous sutf.tt *2 MnSO.«H,0 169.01 2.9S
(7785-87-7)
Manganous di fluoride +2 MnF, 92.93 3.98
17782-&4-U
Manganous trifluoride «
17782-53-11
Manganese borcte *
(12228-91-0)
2 MnF, 111.93 3.54
2 MnB.O,*8H.O 354.17 MS
Manganese formate NS MnCCHO^.'ZH.O 181.00 1.953
Manganese glycerophosphate »2 MnC,H,O.P 225.00 NS
NS NS
stable NS
57-117
856 NS
decomposes NS
600
NS NS
decomposes NS
NS NS
no Solubility
rc>
I
inaoluble tn H,0. Soluble
in anat organic solvents
65 ag/L (25*C)
Soluble in dilute actd
Insoluble in NH, and alcotx
Soluble in alcohol,
Insoluble in ether and MN,
622 g/L (10*C), 1238 g/L
(100'C)
Soluble in cold H.O and
alcohol
Soluble in alcohol
Dacoiapoces in water
Moderately soluble in N,0
Insoluble in H.O
NS
NS
6.6 g/L <40*C), 4.8 g/L
OOO'C) Soluble in acid
Insoluble In alcohol and
ether
Soluble In acid
Decomposes in H,0
Inaoluble fn H,0 or alcohol
Soluble in dilute acid*
Soluble In H,0
Slightly soluble (n cold H
Soluble In acid, citric acid
Insoluble In alcohol
MANGANES.II
11-4
12/07/92
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TABLE
(com.)
R'jgist! y NuiitX'i
'. . * ! • *', ' •
( f'.-ITll C,ll
1 oriiul i!
ManyjnouN hydroxide -j? M
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20°C. Manganous chloride is used as a starting material for other manganese
compounds. The anhydrous form is used as a flux in magnesium metallurgy.
Manganese Ethylenebisdithiocarbamate. (CH2NHCS2)2Mn is a yellow powder
used as a fungicide. It is sold under the name of "Maneb." It is produced by treating
a solution of manganous chloride containing sodium hydroxide and ethylenediamine with
carbon disulfide and neutralizing the resulting solution with acetic acid (U.S. EPA, 1984).
Manqanous Acetate. Mn(C2H3Q2)2«4H2O is a pale red transparent crystal.
Manganous acetate is used as a mordant in dyeing and as a drier for paints and
varnishes. It has a density of 1.589 at 20°C. There is also an anhydrous form of
manganous acetate, which is a brown crystalline substance with a density of 1.74 at
20°C (U.S. EPA, 1984).
Manganous Oxide. MnO is a naturally-occurring compound, known as
manganosite. Manganous oxide has a green cubic crystalline structure with a density
of 543-5.46 at 20°C. It is insoluble in both hot and cold water. It is produced by
reducing higher oxides with either carbon monoxide or coke or by the therrnal
decomposition of manganous carbonate. It can be used as a gcoc starting material 'or
other 'nanganous salts, in ferntes, in welding, and as a nutrient ;n agricultural fe^i'.izers
(U.S. EPA, 1984).
MANGANES.II II-6 02/11/93
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Manganous Phosphate. Mn3(PO4)2 is produced by reacting manganous
carbonate with phosphoric acid. Manganous phosphate is used as an ingredient of
proprietary solutions for phosphating iron and steel (U.S. EPA, 1984).
Manganous Sulfate. MnSO4»H2O is a pale pink monoclinic crystalline structure.
It has a density of 2.95 at 2Q°C. The sulfate can be produced by reacting any
manganese compound with sulfuric acid. The monohydrate form loses all water when
heated to 400-450°C. It is a co-product of the manufacture of hydroquinone. Pure
manganous sulfate is used as a reagent. The majority of manganous sulfate is used as
fertilizer and as a nutritional supplement in animal feeds (U.S. EPA, 1984).
Manganous Soaps. Manganese (II) salts of fatty acids (2-ethyl hexoate, finoleate,
naphthenate, oleate, resinate, stearate and tallate) are used as catalysts for the oxidation
and polymerization of oils and as paint driers (U.S. EPA, 1984).
Other manganese (II) compounds include manganese borate (MnB4O7»8H2O),
which is a brownish-white powder that is insoluble in water and alcohol, yet it
decomposes on long exposure to water. It is used in drying varnishes and oils, as a
drier for linseed oil and also in the leather industry. Manganous difluoride (MnF2) is a
pink, quadratic prism structure or a reddish powder. It has a density of 3.98 at 20°C
and has varying solubilities in water (depending on water temperature). It is made from
manganese carbonate and hydrogen fluoride. Manganous trifluoride (MnFj) is a red
mass of monoclinic crystals with a density of 3.54 at 20°C. It can be easily hydrolyzed
by water. It is used primarily as a fluorinating agent in organic chemistry. Manganese
MANGANES.II II-7 12/07/92
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formate [Mn(CHO2)2»2H2O] is a rhombic crystal with a density of 1.953 at 20°C.
Manganese glycerophosphate (MnC3H7O6P) is a white or slightly red powder.
Manganous hydroxide [Mn(OH)2] is a whitish-pink trigonal crystal with a density of 3.258
at 13°C. It is also known as pyrochao'rte. Manganous nitrate [Mn(NO3)2»4H2O] is a
colorless or rose-colored monoclinic crystal with a density of 1.82 at 20°C. It is used
as an intermediate in the manufacture of reagent grade MnO2 and also in the preparation
of porcelain colorants. Manganous sutfide (MnS) is a green cubic crystal or a pink
amorphous structure. It has a density of 3.99 at 20°C. It is very highly soluble in cold
water and soluble in dilute acid (Weast, 1980; Windholz, 1976).
Manganese (IV) Compounds
Manganese Dioxide. MnO2 is also known as pyrolusite. It is the most important
Mn(IV) compound and the most important commercial compound of manganese.
Pyrolusite is the principal ore of manganese. More than 90% is used in the production
of ferromanganese and other manganese metals and alloys. The other 10% is used to
produce dry cell batteries, chemicals and as an oxidant in the production of some dyes.
It is generally a black crystal or a brown-black powder with a density of 5.026 at 20°C.
Pyrolusite is insoluble in water (U.S. EPA, 1984).
Manganese (VII) Compounds
Potassium Permanganate. KMnO4 is a deep purple or bronze-like, odorless
crystal structure. It is stable in acid and soluble in water with a density of 2.7 at 20°C.
It is used in the organic chemical industry; in the alkaline pickling process; in bleaching
resins, waxes, fats, oils, straw, cotton, silk and other fibers; in dyeing wood brown; with
MANGANES.II II-8 12/07/92
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formaldehyde solution to expel formaldehyde gas for disinfecting; and for water
purification and odor abatement in various industrial wastes (U.S. EPA, 1984).
Summary
Manganese is a brittle, gray-pink metal principally used for alloying with other
metals to impart hardness. It exists in 11 oxidation states with the compounds Mn2*,
Mn4* and Mn7* being the most economically and environmentally Important. Most of
the Mn2* compounds, including manganous carbonate, manganous chloride and
manganous acetate, are soluble in water. The most common Mn4* compound, which
is also the most important commercial compound of manganese, is manganese dioxide
and it is insoluble in water. The Mn7* compound, potassium permanganate, is soluble
in water.
MANGANES.II II-9 12/07/92
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III. TOXICOKINETICS
The absorption, distribution, metabolism and excretion of manganese in the body
has been revfewed by the U.S. EPA (1984). A symposium conducted in 1986 by the
American Chemical Society resulted in a publication entitled Nutritional Bioavailabilrty of
Manganese (Kies, 1987). This volume contains a lot of additional information on the
toxicokinetics of manganese.
Absorption
G»«trojntes«n-l. Cikrt and Vostal (1969) showed that manganese is likely to be
absorbed from the small as well as the large intestine. It is absorbed most efficiently in
the divalent form (Gibbons et al., 1976). Different manganese salts are absorbed with
varying efficiencies, manganese chloride being better absorbed than the sulfate or
acetate (Bales et al., 1987).
Mena et al. (1969) reported findings on Gl absorption of manganese in 11
healthy, fasted human subjects. The subjects were given 100 uCi of ^MnC^ with 200 ^g
stable 55MnC!2 as a carrier. After 2 weeks of daily whole body counts, the absorption of
54Mn was calculated to average -3%. Comparable absorption values were found for
healthy manganese miners and ex-miners with chronic manganese poisoning. However,
enterohepatic circulation was not taken into account in this study; therefore, these values
could be an underestimate of absorption. Thomson et al. (1971) reported a much higher
MANGANES.III 111-1 08/09/93
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absorption rate of ^MnC^ in segments of jejunum and duodenum using a double-lumen
tube. In eight subjects, the mean absorption rate was 27±3%.
Schwartz et al. (1986) studied the absorption and retention of manganese over a
7-week period in seven healthy male volunteers, 22-32 years of age. Relatively high
caloric diets (3100-4400 Kcal/day) were consumed, providing high levels of manganese:
12.0-17.7 mgyday. The authors noted that these levels were high compared with the level
of 2-5 mg/day reported as being safe and adequate by the Food and Nutrition Board of
the National Research Council. During weeks 2-4, manganese absorption was -2.0±4.9%
of the intake and during weeks 5-7 an absorption of 7.6±6.3% was measured. No
explanation was offered for the difference in absorption between these two time points.
Despite the high intakes, there was no net retention of manganese in these individuals;
fecal loss accounted for almost all of the ingested manganese and in some cases was
greater than the intake.
Sandstrom et al. (1986) administered 450 ml of infant formula containing 50 ^g
Mn/L to eight healthy subjects, aged 20-38 years. The absorption from seven of the
subjects was 8.4±4.7% while one subject with an iron deficiency anemia absorbed 45.5%
Six additional subjects were administered 2.5 mg of manganese (as sulfate) in a
multi-element preparation with an absorption of 8.9±3.2%.
In humans administered a dose of radiolabeled manganese in an infant formula.
the mean absorption was 5.9 ± 4.8%, but the range was 0.8-16%. a 20-fold difference
MANGANES.III III-2 08/09/93
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(Davidssonetal., 1989). Retention at day 10 was 2.9±1 8%, but the range was 0.6-9.2%.
again indicating substantial differences between individuals.
Calcium has been suggested to inhibit the absorption of manganese. McDermott
and Kies (1987) have postulated that this inhibition may be due to an effect by calcium
on Gl tract pH. Manganese is more readily absorbed in the +2 valence state and as the
pH rises, oxidation to the +3 and +4 states is favored. Thus, calcium may inhibit
manganese absorption by increasing the alkalinity of the Gl tract. Alternatively, calcium
and manganese may compete for common absorption sites. In contrast to these findings
by McDermott and Kies (1987), Spencer et al. (1979) did not observe any effect of dietary
calcium levels (from 200-800 mg/day) on manganese balance in healthy males.
Dietary phytate, a component of plant protein, was found to decrease the rote, ition
of manganese, possibly as a result of the formation of a complex between manganese
and phytate. which is stable in the intestinal tract (Davies and Nightingale. 1975). Bales
et al (1987) reported that cellulose, pectin and phytate were all found to reduce the
plasma uptake of manganese in human subjects. This may contribute to the decreased
bioavailability of manganese from vegetarian diets. Schwartz et al. (1986) reported that
while no significant correlation was found between phytate intake and manganese
absorption in healthy males, phytate excretion was significantly correlated with
manganese excretion.
MANGANES.III III-3 08/09/93
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Animal studies lead to similar estimates of absorption values. Greenberg et al.
(1343) administered a single oral dose containing G.I rng of ^Mn-labeled manganese (as
chloride) to rats and estimated that 3-4% was absorbed from the intestine. Pollack et al.
(1965) administered a single oral dose of MMn as chloride with 5 Mmoles stable carrier to
fasted rats and reported 2.5-3.5% absorption 6 hours after administration. In separate
studies Rabar (1976) and Kostia! et a!. (1978) administered a singte oral dose of ^Mn as
chloride, carrier free, to postweaning nonfasted rats and reported 0.05% absorption 6
days after administration. This low absorption value may be due to the result of the loss
of absorbed manganese through fecal excretion or to the fact that the rats were not fasted
(U.S. EPA, 1984).
Keen et al. (1986) point out that while others have suggested that a relatively
constant percentage of manganese is absorbed from the intestine, this is only true up to
a point. In suckling rats fed 0.5 mL of infant formulas containing 5 or 25 mg Mn/mL. the
percentage of manganese retained was decreased at the higher level. Saturation of the
absorptive process was also reported by Garcia-Aranda et ai (1983) who studied the
intestinal uptake of manganese in adult rats.
Keen et al. (1986) demonstrated that there is a strong effect of age on intestinal
manganese uptake and retention. Sprague-Dawley rat pups were fasted overnight and
then intubated with 0.5 mL of human milk containing 5 ^g ^Mn/mL Manganese retention
was highest (>80%) in pups <15 days old. In older pups (16-19 days old), the average
retention was 40%. Infant formulas were also administered to rat pups. Soy formula
MANGANES.III III-4 08/09/93
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contains a much higher level of Mn than does human milk with the amount of manganese
retained in 14-day-old rat pups being 25 times higher from soy formula compared with
human milk. Chan et al. (1987) also demonstrated that the developmental stage of the
rat has a big influence on the absorption of manganese. From age 9 days to 20 days
there is a decline in the amount of manganese absorbed, which is correlated with a switch
in the site of maximal absorption. Tne duodenum is more active in manganese uptake
in younger rats while the jejunum becomes more important as the animals mature.
Chan et al. (1987) also reported a large variation in the concentration of
manganese from different milk sources. Human milk contained only 8±3 Mg Mn/L while
bovine milk, infant formula and rat milk contained 30±5, 73±4 and 148±18 ng Mn/L.
respectively. However, these absolute quantities may not reflect the actual amount of
bioavailable manganese as indicated by the comparable absorption of manganese from
these four types of milk in suckling rats. In an earlier study, Chan et al. (1982) determined
that the chemical form of manganese in infant formula is very different from that in human
or cow milk Human and cow milk contain two and three manganese-binding proteins.
respectively All manganese in these milks is protein bound while the manganese in
infant formulas is in the form of soluble salts. The degree to which the chemical form of
manganese affects bioavailability is not known.
Ldnnerdal et al. (1987) also reported that age, manganese intake and dietary
factors all affect manganese absorption ind retention. Retention is very high during the
neonatal period and decreases considerably with age because of both decreased
MANGANES.III 111-5 08/09/93
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absorption and increased excretion in the bile. In young rat pups, the bioavailability of
managanese from various milk sources varied, with greater absorption occurring from
human milk and cow's milk formula than from soy formula. These differences were not
as pronounced in older pups.
Manganese appears to be absorbed in the +2 valence state and competes with
iron and cobalt for the same absorption sites (Thomson et al., 1971). Animal studies
have demonstrated an effect of iron deficiency on manganese uptake. Rehnberg et al.
(1982) administered dietary Mn3O4 (450, 1150 or 4000 ppm Mn) to young rats. Using
basal diets either sufficient or deficient in iron, it was shown that iron deficiency promotes
the intestinal absorption of manganese. Conversely, manganese absorption is inhibited
by large amounts of dietary iron. Gruden (1984) demonstrated that 3-week-old rat pups
given a high concentration of iron in cow's milk (103 ^g/mL) absorbed 50% less
manganese than pups receiving the control milk (0.5 ^g Fe/mL). This difference was not
seen in rats tested at 8, 11. 14 or 17 days of age, suggesting that the inhibition of
manganese absorption by iron develops quickly in rats in the third week of life
Respiratory. Although there appear to be no quantitative data on absorption rates
following inhalation of manganese, the Task Group on Metal Accumulation (TGMA, 1973)
considered some basic principles that may be applied to inhaled metals. Small
particles (<1 ^m) reach the alveolar lining and are likely to be absorbed directly into the
blood. Of the inhaled metal initially deposited in the lung, a portion is thought to be
removed by mucociliary clearance and swallowed, consequently entering the Gl
MANGANES.III III-6 08/09/93
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absorption process. The single study of respiratory absorption of manganese, performed
by Mena et al. (1969), was reviewed in U.S. EPA (1984) and was noted to be lacking in
complete experimental data.
Distribution
Studies of the distribution of manganese in humans are generally based upon
post-mortem analyses of various organs and tissues. They reflect the body and organ
burden of a lifetime intake of manganese. Both Cotzias (1958) and WHO (1981) reported
a total of 12-20 mg manganese in a normal 70 kg man, while Sumino et al. (1975)
reported an average of 8 mg among 15 male and 15 female cadavers with an average
weight of 55 kg. The highest concentrations of manganese in the body of persons without
undue exposure have been found in the liver, kidney and endocrine glands with lesser
concentrations found in the brain, heart and lungs. Perry et al. (1973) found little variation
in manganese concentration from one part of the liver to another. Regional studies of the
distribution of manganese in the brain by Larsen et al. (1979) and Smeyers-Verbeke et
al. (1976) have reported the highest concentration in the basal ganglia.
Animal study results have generally shown agreement with the pattern of tissue
distribution revealed in human studies (U.S. EPA, 1984). In mice, Kato (1963) reported
a high uptake of radioactive manganese by the liver, kidneys and endocrine glands and
a lesser amount in brain and bone. This study and a study by Maynard and Cotzias
(1955) found that tissues rich in mitochondria (for example, liver, kidney and pancreas)
contained higher levels of manganese. Similarly in mice, Mouri (1973) reported that the
MANGANES.III III-7 08/09/93
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highest concentrations of manganese occurred in the kidney, liver, pancreas and brain
both 8 and 15 days after inhalation of manganese. In rats, after an intraperitoneal dose
of radioactive manganese, Dastur et al. (1969) found the highest concentrations in the
suprarenal, piruitary, liver and kidney tissue. Scheuhammer and Cherian (1981) reported
findings on the distribution of manganese in male rat brain tissue with and without
intraperitoneal exposure to 3 mg Mn/kg as MnCI2. In unexposed rats the highest
concentrations of manganese were found in the hypothalamus, colliculi, olfactory bulbs
and midbrain. In treated rats all brain regions showed an increase in manganese; the
highest concentrations were found in the corpus striatum and corpus callosum. In
monkeys exposed intraperitoneally to manganese, Dastur et al. (1971) found the highest
concentrations to be in liver, kidney and endocrine glands. In monkeys injected
subcutaneously with manganese, increased concentrations were found in the tissues of
the endocrine and exocrine glands (thyroids, parotids and gall bladder) and in the nuclei
of cerebral basal ganglia (Suzuki et al., 1975).
The distribution of manganese in the body appears to differ depending on the route
of administration Autissier et al (1982) reported that rats given a daily intraperitoneal
dose of 10 mg/kg manganese chloride for 4 months showed significant increases in the
accumulation of manganese in the brain. The study showed a 359% increase in the
concentration of manganese in the brain stem, 243% in the corpus striatum, and 138%
in the hypothalamus. In rats given drinking water containing 278 ppm MnCI2 for 2 years,
Chan et al. (1981) found a 31% increase in manganese concentrations in the brain and
a 45% increase in liver relative to control values.
MANGANES.III III-8 08/09/93
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The form in which manganese is administered may also have an effect on its
subsequent tissue distribution. Gianutsos et al. (1985) demonstrated in mice that blood
and brain levels of manganese are increased following i.p. injection of manganese
chloride (MnCI2), manganese oxide (Mn3O4), or methylcyclopentadienyl manganese
tricarbonyl (MMT). However, MnC^ administration resulted in faster and higher levels of
blood and brain manganese. It was suggested that the differences seen among the
three manganese compounds are due to the oxide and MMT forms being more
hydrophobia. This may result in a depot being formed at the site of injection so that
absorption is retarded. It was also demonstrated that the exit of manganese from the
brain is a slower process than its entry, resulting in a long retention period and potential
accumulation. A single injection of 0.4 meq Mn/kg resulted in a significant increase
(>2-fold) in brain levels within 1-4 hours and the high levels were maintained for at least
21 days. Brain manganese levels were especially sensitive to repeated treatment with
a much greater accumulation resulting from the dose being divided into 10 injections
given every other day as compared with a single injection. This may be related to the
slow onset of manganese neurotoxicrty; an acute exposure may result in other organs
serving as the primary target while a chronic exposure results in gradually increasing brain
levels with subsequent neurotoxicity.
The tissue distribution of manganese is also affected by co-exposure to other
metals. Shukla and Chandra (1987) exposed young male rats to lead (5 mg/L in
drinking water) and/or manganese (1 or 4 mg/kg, i.p.) for 30 'lays. They reported that
exposure to the metals individually resulted in accumulation in all brain regions, but
MANGANES.III 111-9 08/09/93
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co-exposure to lead and manganese further increased levels of both metals, especially
in the corpus striatum. Administration of manganese alone led to dose-dependent
increased levels in liver, Kidney and testis. Co-exposure to lead further increased
manganese accumulation in liver. It was concluded that the interaction of metals can alter
tissue distribution and that adverse health effects may result from co-exposures to even
low levels of metals.
Human studies by Schroeder et ai. (1966) and Widdowson et al. (1972) confirm
that placenta! transfer of manganese takes place. While most manganese levels in the
fetus and newborn were reported to be similar to adult levels, fetal bone manganese
concentration was reported to be higher than in the adult. In animal studies, neonatal
mice, rats and kittens were found to very rapidly accumulate manganese without excreting
it in the first 18 days of life (U.S. EPA, 1984). However, when lactating rats and cats were
given excessive doses of manganese in drinking water (>280 mg/L), their offspring
initiated excretion before the 16th day of life.
Kontur and Fechter (1985) demonstrated placenta! transfer of manganese in Long
Evans rats exposed throughout gestation However the transfer was limited with only
0 4% of manganese accumulating in a single fetus. Neonatal rats of exposed dams did
have significantly increased levels of manganese in the forebrain. but this was not
associated with any toxicity.
MANGANES.W 111-10 08/09/93
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in
a
in another study, rat pups showed a greater accumulation of manganese in the
brain, but not in the liver, than did their mothers (Kostial et al., 1978). Rehnberg et al.
(1980, 1981, 1982) reported similar results showing that the neonatal brain reaches
higher concentrations of manganese than other tissues. This could be a response to a
nutritional need. The relationship to toxicrty is unclear.
Normal values in humans reported for the concentration of manganese in whole
blood range from 7-12 ^gfl (U.S. EPA, 1984). In most cases, manganese blood levels
exposed and unexposed workers have not differed significantly. This is supported by
study by Tsaiev ei ai. (1977) that found workers exposed to -1 mg Mn dusi/rn3 air for
1-10 years had blood levels of manganese averaging 11-16 ^gJL compared with a mean
of 10 MgA. in unexposed workers.
Roels et a!. (1987b) found that workers exposed to an average of -1 mg/m3 Mn
dust (range = 0.07-8.61 mg/m3) for 1-19 years had a blood manganese concentration of
0.1-3.59 ^g/100 ml (arithmetic mean = 1.36) while a group of control workers had
levels ranging from 0.04-1.31 ^g/100 ml_ (mean = 0.57). Levels of manganese in the
urine ranged from 0.06-140.6 (geometric mean = 1.56) ug/g creatinine in exposed workers
while levels ranged from 0.01-5.04 (mean = 0.15) ug/g creatinine in controls. On a group
basis, a correlation does exist between blood manganese and past exposure and also
between urine manganese and airborne manganese levels. However, no relationship
was found between blood and urine manganese concentrations and neither level
MANGANES.III 111-11 08/09/93
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correlated on an individual basis with the current level of airborne manganese or the
duration of manganese exposure.
Hagenfeldt et al. (1973) found variations in plasma manganese concentrations in
women and suggested the variation may be due to hormonal changes. Horiuchi et al.
(1967) and Zhemakova (1967) found no difference in the concentration of manganese in
the blood of men and women. Slight seasonal (lower during summer and autumn) and
diurnal (lower during night) variations in blood manganese concentrations have also
been reported (U.S. EPA, 1984).
The concentration of manganese in blood and urine has not proven to be a reliable
indicator of exposure (Roels et al., 1987b; U.S. EPA, 1984). In addition, only a single
study by Horiuchi et al. (1970) showed a positive correlation between manganese blood
and urine levels and the finding of neurologic symptoms and signs. Jindrichova (1969)
recommended the determination of manganese in feces for evaluation of exposure. Since
biliary excretion is the major route of elimination, the amount in the feces seems to be a
reliable measure of exposure.
Alternatively, hair concentrations of manganese may be a more reliable indicator
of environmental exposure. In such an analysis, caution must be exercised to account
for differences that could be attributed to age, sex, race, hair color and hair treatment.
(Sky-Peck, 1990). With propei control groups to be used for comparisons, hair
concentrations of manganese may be reflective of increased exposures as demonstrated
MANGANES.III 111-12 08/09/93
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in the epidemiologic study of manganese in drinking water by Kondakis et al. (1989). This
study is decribed in Chapter 6.
Metabolism
Manganese is an essential element for many species, including mammals.
Although the daily requirement of manganese for development and growth has not been
adequately studied, it was accepted that diets containing 50 mg/kg manganese are
adequate for most laboratory animals (MAS, 1978; Rogers, 1979). Assuming a food
consumption equivalent to 5% of body weight, this corresponds to a requirement for
about 2.5 mg Mn/kg bw/day. Manganese requirements for humans have not been fully
determined. However, the Food and Nutrition Board of the National Research Council
(NRC, 1989) estimated an "adequate and safe" intake of manganese to be 2-5 mg/day
for adults, or about 0.03-0.07 mg Mn/kg bw/day, assuming a reference body weight of
70 kg. The dietary requirement for manganese in rats then, may be about 2 orders of
magnitude higher than the estimated safe and adequate intake for humans.
Manganese is a constituent of the enzymes pyruvate carboxylase and superoxide
dismutase, and is required for the activation of many enzymes. Most of the glycosyl
transferases, which synthesize potysacchandes and glycoproteins, require manganese
for normal activity (Leach, 1971, 1976). Experimental evidence suggests that an
impairment in glycosaminoglycan metabolism is associated with symptoms of manganese
deficiency (Leach and Lilbum, 1978). Manganese has been shown to stimulate the
MANGANES.III 111-13 08/09/93
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synthesis of chondroitin sulfate, contained in cartilage and connective tissue (Piscator.
1979).
Manganese is removed from the blood very efficiently by the liver after binding
to an a2-macroglobulin in the portal blood. Some manganese becomes bound to
transferrin. The metabolism of manganese is controlled by homeostatic mechanisms at
the levels of excretion and absorption. These mechanisms respond very efficiency to
increases in manganese concentration (U.S. EPA, 1984).
Normal manganese metabolism varies with the potential for interaction with other
metals in the body and the age of the individual. Iron deficiency has been shown to
enhance the absorption of manganese in both humans and animals (U.S. EPA, 1984).
Studies have found that manganese competes with iron and cobalt in the process of
uptake from the lumen into the mucosal cells and in the transfer across the mucosa into
the body (U.S. EPA, 1984).
Fxcretion
Manganese is excreted almost exclusively in the feces of humans and animals
Both the WHO (1981) and Newbeme (1973) have reported that human excretion of
manganese in urine, sweat and milk is minimal.
MANGANES.III 111-14 08/09/93
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Price et at. (1970) reported that for preadolescent girls consuming 2.13-2.43 mg
Mn/day, 1.66-2.23 mg/day was excreted in the feces and 0.01-0.02 mg/day was excreted
in the urine.
Although the kidney is not an important route of excretion for inorganic species.
some manganese is found in the urine. The normal level of manganese found in urine
of humans has been reported to be 1-8 ^g/L but values as high as 21 ^g/L have also been
reported (U.S. EPA. 1984).
Tanaka and Lieben (1969) found a rough correlation in humans between mean
urine levels and the average concentration of manganese in workroom air however, the
correlation was poor in individual cases. Similarly, both Horiuchi et al. (1967) and
Chandra et al. (1981b) reported an association between mean urinary manganese levels
and increased levels of manganese in air.
In early animal studies of manganese excretion, Greenberg and Campbell (1940)
reported that 90.7% of a 1 mg intraperitoneal dose of manganese (**Mn) was found in rat
feces within 3 days. In a subsequent study using rats. Greenberg et al. (1943) found that
27 1% of a 0.01 mg intraperitoneal dose of manganese (^Mn) and 37.3% of a 0.1 mg
dose were collected in bile within 48 hours. Later studies have confirmed that bile is the
main route of excretion of manganese and represents the principal regulatory mechanism.
Tichy et al. (1973) administered a dose of 0.6 Mg manganese chloride to rats and reported
that 27% was excreted into bile within 24 hours. Klaassen (1974) administered increasing
MANGANES.III 111-15 08/09/93
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doses (0.3, 1.0. 3.0, 10.0 mg/kg bw) of manganese to rats, rabbits and dogs. The
concentration of manganese in bile was 100-200 times higher than in plasma at the three
lower doses. As the dose increased, the excretion of manganese into the bile was found
to increase. However, after the 10.0 mg dose there was no further increase in excretion
of manganese into the bile and a maximum excretion rate of 6.5 ^g/min/kg was attained,
indicating that a saturabte active transport mechanism may exist (U.S. EPA, 1984).
Klaassen (1974) also reported urinary excretion to be low.
Experiments in animals by Bertinchamps and Cotzias (1958), Kato (1963) and
Papavasiliou et al. (1966) have shown that manganese is also excreted through the
intestinal wall. This has been found to be particularly true in the presence of biliary
obstruction or with overloading of manganese. Bertinchamps et al. (1966) and Cikrt
(1973) have also reported that in rats the excretion of manganese through the intestinal
wall into the duodenum, jejunum and terminal ileum may take place. In dogs, Burnett
et al (1952) have shown manganese to be excreted with the pancreatic juice.
In human studies of the biologic half-time of manganese in the body, Mahoney
and Small (1968) reported a biphasic clearance of intravenously injected MnCI2. the rapid
phase being 4 days and the slow phase lasting 39 days. Sandstrbm et al. (1986)
reported biologic half-life values of 13±8 days and 34±8 days in 14 healthy subjects
given manganese orally. Two subjects were also administered manganese intravenously
and had a much slower turnover. Schroeder et al. (1966) reported a whole body
MANGANES.III 111-16 08/09/93
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turnover rate in healthy adults of about 40 days with a total body manganese content of
about 20 mg.
Cotzias et al. (1968) injected manganese intravenously and reported a biologic
half-time of 37.5 days in healthy subjects, 15 days in healthy miners and 28 days in
those with chronic manganese poisoning. The study also found that, in healthy subjects,
clearance from the liver averaged 25 days; from the head 54 days; and from the thigh
57 days. In healthy miners, liver clearance averaged 13 days; head, 37 days; and thigh,
39 days. Those with chronic manganese poisoning cleared manganese from the liver
in 26 days, from the head in 62 days and from the thigh in 48 days.
The clearance of manganese in primates was studied by Newland et al. (1987).
Following a 30-minute inhalation of trace amounts of ^MnC^ aerosol by two female
macaque monkeys, radioactivity was monitored for over a year in the chest head and
feces. Levels of radioactivity in the chest remained elevated throughout the experiment.
Three half-times, ranging from 0.2-187 days, were needed to describe the clearance of
manganese from the chest. Fecal excretion of manganese was described by two
half-times of <1 day and 50-60 days Head levels peaked 40 days after exposure and
remained elevated for over a year. Clearance of manganese from the head was
described by a single half-time of -245 days. This slow clearance was attributed both
to the slow disappearance of manganese from the head and to replenishment from other
tissues, particularly the lung. A third monkey was administered a subcutaneous dose
of ^MnClj and clearance from the head was 4.5 times faster. This study demonstrates
MANGANES.III 111-17 08/09/93
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that lung deposits can prolong elevated brain levels and this may account for the
occurrence and progression of manganism after inhalation exposure has ended.
In animal studies, both Britton and Cotzias (1966) and Suzuki (1974) found that
an increase in dietary intake of manganese decreased biologic half-times. Studies also
indicate that the biologic half-time of manganese in the brain of rats, mice and monkeys
is longer than that in the body (Suzuki, 1974; Dastur et al., 1969,1971).
Homeost*sis
As pointed out by Rehnberg et al. (1980), the normal human adult effectively
maintains tissue manganese at stable levels despite large variations in manganese
intake. Although some investigators maintain that this homeostatic mechanism is based
on controlled excretion, a critical review of the evidence reveals that regulation of
manganese levels also occurs at the level of absorption (U.S. EPA, 1984).
Summary
Manganese is absorbed from the Gl tract after being ingested Human and
animal studies estimate that -3-9% of the ingested manganese is absorbed with values
being higher for suckling animals (Mena et al., 1969, Greenberg et al., 1943: Sandstrom
et al., 1986; Keen et al., 1986). A portion of inhaled manganese may be swallowed and
subsequently absorbed from the Gl tract. There are no definitive data, however, on
absorption rates following the inhalation of manganese.
MANGANES.III 111-18 08/09/93
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A total of 12-20 mg has been reported to be the normal body burden of manganese
in a 70 kg man (WHO, 1981), with the highest concentrations occurring in the liver, kidney
and endocrine glands of both humans and animals (WHO, 1981; Kato, 1963). In animals,
the distribution of excess manganese in the body appears to differ depending on the route
of administration. Intraperitoneally administrated manganese has been shown to increase
the accumulation of manganese in the rat brain more than that orally administered
(Autissier et al., 1982; Rehnberg et al., 1982; Chan et al., 1981).
Studies have confirmed that the placenta! transfer of manganese takes place, and
have concluded also that the neonatal brain may be at a higher risk of accumulating
excess manganese than are other tissues (Schroeder et al., 1966; Kostial et al., 1978).
Normal human values for manganese in whole blood range from 7-12 t*g/L, and
in most cases do not differ for exposed and nonexposed individuals (U.S. EPA, 1984).
Thus, the level of manganese in blood is not a good indicator of manganese exposure.
Concentrations in hair are considered to be more reliable (Sky-Peck, 1990).
Manganese is an essential element that is a constituent and activator of many
enzymes. There are no well-defined occurrences of manganese deficiency in humans,
but deficiency has been demonstrated in laboratory mice, rats, rabbits and guinea pigs
(U.S EPA, 1984) The main manifestations of manganese deficiency are those
associated with skeletal abnormalities, impaired growth, ataxia of the newborn, and
defects in lipid and carbohydrate metabolism.
MANGANES.III 111-19 08/09/93
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Under normal circumstances of exposure, manganese is efficiently controlled in the
body by homeostatic mechanisms. Excess manganese exposure may be most toxic to
the brain, where CMS effects are related to alterations in levels of brain monoamines. The
appropriateness of using rodents to model the CMS effects observed in humans has
been questioned. Pigmented brain tissue, which more readily accumulates manganese,
is more characteristic of primates than of rodents (U.S. EPA, 1984).
Bile is the main route of manganese excretion and represents the principal
regulatory mechanism. Minimal excretion has been reported to occur in urine, sweat
and milk (Klaassen, 1974). Manganese is also excreted through the intestinal wall,
especially in the presence of biliary obstruction or overloading of manganese.
Increased manganese intake has been shown to decrease biologic half-times.
A biologic half-time of 37.5 days has been reported for healthy subjects and 28 days for
subjects with chronic manganese poisoning (Cotzias et a!., 1968). Brain biologic
half-times appear to be longer than in the rest of the body (Suzuki, 1974)
MANGANES.III III-20 08/09/93
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V. HEALTH EFFECTS IN ANIMALS
General Toxicfty
Acute Toxlclty. Information on the LD^ and LD10 values will be presented for
oral, parenteral and s.c. exposures, while LC^ and LC10 values will be presented for
inhalation exposure for various manganese compounds. The toxicity of manganese
varies with the chemical form, with the insoluble oxide being less toxic than the soluble
forms. This information was obtained primarily from a review of U.S. EPA (1984) and
NIOSH (1984).
Ora| - Oral LD^ values observed in animal experiments are presented in Table
V-1 and range from 10 mg Mn/kg for exposure to MMT (methylcyclopentadienyl
manganese tricarbonyl) in rats to 2197 mg Mn/kg bw for exposure to manganese
dioxide in rats. Manganese toxicity may vary not only with route of exposure and
chemical compound, but also with the age, sex and species of animal. For example,
studies by Hinderer (1979) indicate that female rats and mice are more sensitive to MMT
by the oral route of exposure than male rats and mice. In addition, rats were reported
to be more sensitive to MMT oral exposure than mice (Hinderer, 1979). Kostial et al.
(1978) found that MnCI2 produced the greatest oral toxicity in the oldest and youngest
groups. Rothand and Adleman (1975) suggest that for the older rats, increased
susceptibility to manganese toxicity may be due to a decrease in adaptive
responsiveness, which is characteristic of the aging process. Increased sensitivity
among the younger rats may be the result of higher intestinal absorption and body
retention of manganese.
MANGANES.V V-1 12/10/92
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TABLE V-1
Oral LD-o Values for Manganese Compounds
Compound
Methylcyclopentadienyl
manganese tricarbonyl
(MMT)
Cyclopsntadieny!
manganese tricarbonyl
Manganese chloride
Species
LD
so
Manganese acetate
Manganese dioxide
Potassium
permanganate
rat
rat
rat
mouse
rat
rat
rat
rat
mouse
guinea pig
rat
rat
mouse
rat
rat
(mg Mn/kg bw)
10
12
12
48
22
425
475
410
450
400
836
2197
750
379
750
guinea pig
810
Reference
Hanzlik et al., 1980
Hinderer, 1979
Hyseil et ai., 1974
Hinderer, 1979
Penney et a!., 1985
Sigan and Vitvickaja,
1971
Kostia! et al, 1978
Holbrook et a!., 1975
Sigan and Vitvickaja,
1971
Sigan and Vrtvickaja,
1971
Smyth et a!., 1969
Holbrook et al., 1975
Siaan and Vrtvickaia.
19~71
Smyth et al., 1969
Sigan and Vitvickaja,
1971
Sigan and Vitvickaja,
1971
MANGANES.V
V-2
12/10/92
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Parentera! - Generally, parenteral routes produce mortality at tower doses than
do oral exposures. Pa-entera1 LD^ values are presented in Table V-2 and range from
14-64 mg Mn/kg bw. In comparative intraperitoneai toxicity studies, Franz (1962) and
Bienvenu et al. (1963) have shown that manganese is less toxic than many other metals.
Baxter et al. (1965) measured a number of physiologic parameters in rats
(100-550 g) 1-72 hours after s.c. administration of 5-150 mg of manganese as MnCU.
diluted in normal saline. Levels of hemoglobin, hematocrit and mean corpuscular volume
were significantly increased in rats receiving 15 mg Mn/100 g bw. The peak increase
in these parameters occurred at 12 and 18 hours after dosing. The maximum response
occurred at 170-300 mg Mn/kg. A measurable response occurred at 50 mg Mn/kg.
Necrotic changes were noted in hepatic tissue 18 hours after a single dose of 170 mg
Mn/kg.
Subchronic and Chronic Toxicity. Epidemioiogic studies of chronic manganese
intoxication in exposed workers indicate that the CMS is the major target, and that the
pulmonary system may also be affected. To a lesser extent hematologic, cardiovascular
and digestive system effects may also occur. This chapter will cover the effects of
chronic exposure to manganese on systemic toxicity and carcinogenic, mutagenic,
reproductive and teratcgenic effects in animals.
In humans, the overt CNS effects of manganese exposure result from an
extrapyramidal neurologic dysfunction. Some of these signs resemble those associated
MANGANES.V V-3 12/10/92
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TABLE V-2
Parenteral LDM Values for Manganese Compounds
Compound
Cydopentadienyl
manganese tricarbonyl
Manganese chloride
Species Route of LD^, Reference
Administration (mg/kg bw)
Manganese sulfate
Manganese sulfate,
tetrahydrate
Manganese nitrate
rat
rat
mouse
mouse
mouse
mouse
i.p.
i.p.
i.p.
i.p.
i.p.
i.p.
14
38
53
44
64
56
Penney et al
1985
Franz, 1962;
Holbrook
et al., 1975
Franz, 1962;
Holbrook
et al., 1975
Bienvenu
et al., 1963
Yamamoto
and Suzuki,
1969
Yamamoto
and Suzuki,
1969
MANGANES.V
V-4
12/10/92
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with Parkinsonism and include muscular rigidity and lack of coordination. Other reported
signs more cioseiy resemble some forms of dystonia. Barbeau (1984) summarized the
similarities and differences between manganism and Parkinsonism and suggested that
manganism, rather than a model of Parkinsonism, is a mixture of extrapyramidal
bradykinesia and dystonia.
Studies conducted to mode! this disease in small laboratory animals are open to
some question since one must reiy upon analogous, not homologous behaviors. Aiso,
as discussed in Chapter III, the accumulation and neurotoxicity of manganese may differ
for rodents as compared with primates. Among other differences, primate brain tissue
contains more pigmented areas that favor manganese accumulation than rodent brain
tissue. Moreover, the overt neurologic impairment in primates is often preceded or
accompanied by psychologic symptoms, such as irritability and emotional lability, that
are not evident in rodents.
There may also be significant species differences in the requirements for
manganese as an essential element. The NRC (1989) has determined a safe and
adequate intake of 2-5 mg Mn/day for adults. Assuming a body weight of 70 kg, this
range is equivalent to about 0.03-0.07 mg Mn/kg/day for humans. Rodents require
greater intakes of manganese: 50 mg/kg diet for rats and 45 mg/kg diet for mice
(National Research Council, cited in NTP, 1992). Assuming a food consumption of 5%
of body weight per day for rats and 13% for mice (U.S. EPA, I986b), these dietary
concentrations are equivalent to 2.5 mg Mn/kg bw/day for rats and 5.85 mg Mn/kg
bw/day for mice, about 100 times higher than the requirement for humans.
MANGANES.V V-5 02/24/93
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Studies using monkeys show results consistent with the hypothesis that chronic
manganese exposure results primarily in disturbances of the CMS, The U.S. EPA (1984)
reported that there are insufficient data to determine an accurate dose-response
relationship for the neurologic effects of chronic inhalation exposure to manganese.
Oral Exposure. In a 14-day study, NTP (1992) administered diets containing 0,
3130, 6250, 12,500, 25,000 or 50,000 ppm manganese sulfate monohydrate (-33%
manganese) to groups (5/sex/dose) of B6C3F1 mice and F344 rats. All rats survived
the exposure period. High-dose males had a final mean body weight that was 13%
lower, and a mean body weight gain that was 57% lower than controls. High-dose
females had a final mean body weight that was 7% lower, and a mean body weight gain
that was 20% lower than controls. These groups also exhibited diarrhea during the
second week of the study. No other effects attributed to manganese exposure were
reported in any group of mice.
Neurotoxic Effects - Studies of rodents exposed to manganese by drinking
water or food have not been able to produce the characteristic signs of extrapyramidal
neurologic disease seen in humans. For example, Gray and Laskey (1980) found that
dietary exposure to HOC ppm manganese (as Mn3OJ in rats for 2 months produced
only reduced reactive locomotor activity (RLA).
Accurate dose-response relationships based upon neurobehavioral endpoints,
which are characteristic of chronic manganese exposure in humans, are not available
from animal studies. Neurochemical responses, however, may offer useful ancillary
MANGANES.V V-6 02/10/93
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information. Such studies have been based largely upon the supposition that since the
toxic manifestations of chronic manganese exposure resemble Parkinsonism. altered
biogenic amine metabolism in the CMS may be one of the underlying mechanisms.
However, the effects reported, for example on the level of dopamine as affected by
manganese exposure, are not consistent from one study to another. While manganese
exposure is generally considered to result in decreased dopamine levels, some studies
report increases, while others report effects that change over time.
Singh et al. (1979) administered manganese (16 mg/kg bw in a 10% sucrose
solution) alone or in combination with ethanol to groups of 20 male albino rats for 30
days. The manganese exposure alone led to a 72% increase in manganese
concentration in the brain (3.13 ng/g dry weight vs. 1.82 ng/g for controls). This was
not affected by ethanol exposure. There were no morphologic changes in the brain
tissue of any group; however, significant alterations were reported for several brain
enzymes. Manganese exposure resulted in significant increases in monoamine oxidase
(p<0.001), adenosine triphosphatase (p<0.00l), ribonudease (p<0.001),
glutamate-oxaloacetate transaminase (p<0.01). Significant decreases were reported for
succinic dehydrogenase (p<0.02) and deoxyribonuclease (p<0.00l). Several other
enzymes were not affected. Concurrent exposure to ethanol resulted in a synergistic
effect with some enzymes and an antagonistic effect with others. The authors were not
able to suggest a definitive role for ethanol ingestion with regard to simultaneous
manganese exposure.
MANGANES.V V-7 02/24/93
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Deskin et al. (1980) studied neurochemical alteration induced by manganese
chloride in neonatal CD rats. Rats were intubated daily with 1, 10 or 20 ng Mn/g from
birth to 24 days old. Neurochemical components were then analyzed in the
hypothalamic area and corpus striatum. Manganese administration (10 and 20 jig/g)
resulted in a significant elevation of manganese in both regions of the brain, but
neurochemical alterations were observed only in the hypothalamic area. These
alterations included a decrease in dopamine concentration and turnover. The highest
dose also resulted in a significant decrease in hypothalamic tyrosine hydroxylase activity
and an increase in monoamine oxidase activity. There were no visible signs of toxicity
in any group. A subsequent study by Deskin et al. (1981) using the same protocol (but
doses of 10, 15 or 20 M9/9) reported a significant elevation in serotonin levels in the
hypothalamus, but not the striatum, following exposure to 20
Kontur and Fechter (1988) intubated neonatal Long-Evans rats daily with 0, 25 or
50 /ig/g manganese chloride (MnC12»4H20) for 14 or 21 days. The level of manganese
in the brain was increased at both 14 and 21 days, but was greater at 14 days.
However, monoamine and metabolite levels were not altered by manganese treatment
in any region at either age. The authors suggest that the different results reported by
different laboratories may be because of species or strain differences, the dosing
regimen or vehicle, the route of administration, or the time points chosen for testing.
Whether neurochemical indices, such as changes in the level of dopamine, can
serve as a direct toxic assay may be debated. Silbergeld (1982) suggests that the
earliest detectable expressions of neurotoxicity for many substances, including
MANGANES.V V-8 02/24/93
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manganese, are likely to be behavioral and that altered behavior represents a functionally
significant outcome. If the mechanism is assumed to be biochemical or morphologic
aberrations, then behavioral indices may be used as a measure of adverse effects.
Chandra et al. (1979a) found elevated levels of striatal dopamine, norepinephrine
and homovanillic acid with a concomitant increase in spontaneous tocomotor activity at
60 and 90 days of age in mice exposed to manganese from birth. While suckling, the
mice were exposed by their lactating dams, which were exposed to MnCI2 (5 mg/mL)
in their drinking water. The mice were weaned at 25 days and subsequently received
drinking water exposures to manganese that were determined, on average, to be 30 M9
Mn/day for 60 days, 36 ng Mn/day through the 90th day, 75 /ig Mn/day through the
120th day and 90 /ig Mn/day for_<.150 and 180 days. Exposure past 90 days did not
influence motor activity. Chandra et al. (1979a) suggest that the hyperactivity observed
in mice may be an early behavioral effect of excess manganese exposure and resultant
dopamine and norepinephrine elevations, comparable with the early psychotic phase in
humans exposed to manganese. Although in this experiment the levels of brain biogenic
amines were comparable with controls after 90 days of exposure, other investigators
have noted that continued exposure to manganese produces a marked decrease in
brain biogenic amines, especially dopamine (Bonilla and Diez-Ewald, 1974). In a later
experiment using rats, Chandra and Shukla (1981) did find initial increases in dopamine,
norepinephrine and homovanillic acid followed by a period of normal levels, and after 300
days, a decrease in all levels. In addition, accompanying behavioral studies found an
initial increase in spontaneous locomotor activity followed by a decrease during later
periods of manganese exposure (Ali et al., 1981).
MANGANES.V V-9 12/31/92
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Chandra and Shukla (1981) suggested that decreased locomotor activity observed
during later periods of manganese exposure may be related to lowered dopamine and
norepinephrine levels in the brain, and that this stage of chronic toxicity may correspond
to the later neurologic phase of motor dyskinesias in humans.
Kristensson et al. (1986) studied the effect of manganese on the developing
nervous system of young rats. Starting at 3 days of age, Sprague-Dawley rats were
given a daily dose of 150 mg Mn/kg bw (as MnCI2) by gavage for_<44 days of age. At
15-22 days of age there was a large but transient increase (7-40 fold) of manganese in
the brain, and the rats displayed a rigid and unsteady gait. By 44 days, the rats
appeared normal and brain manganese levels had declined to only 3 times the control
level. Histologic analysis revealed no abnormalities in the brains of rats exposed to
manganese. Axonal growth and the axon-myelin relation were also found to be normal.
Another group of rats was treated for only 15 days at which time half were sacrificed and
half were maintained untreated until 60 days of age. These rats were analyzed for brain
content of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and
homovanillic acid (HVA), and serotonin (5-HT) and its major metabolite,
5-hydroxyindolacetic acid (5-HIAA). Of these, only HVA levels in the hypothalamus and
striatum were affected by manganese treatment. However, the significantly decreased
HVA levels were seen only at the 15-day sacrifice. The rats that were treated 15 days
and then maintained without manganese treatment until 60 days of age were not different
from controls. The investigators concluded that divalent manganese has a very low
degree of toxicity for the developing nervous system in rats but that a longer-term
exposure to more active manganese compounds may cause severe damage to certain
MANGANES.V V-10 12/31/92
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neurologic pathways. They also emphasize that rodents may not be appropriate for
comparison with primates, as their unpublished studies with monkeys exposed to
manganese oxide reveal severe motor disturbances.
Eriksson et al. (1987) studied the effect of long-term manganese exposure on
biogenic amine levels in rat brain. Starting at 20 days of age, groups of male
Sprague-Dawley rats were provided with drinking water containing 10 g/L manganese
chloride (MnC12»4H20) for 60, 100, 165 or 265 days. There were no clinical signs of
poisoning. Following 60 days of exposure, manganese concentration in the striatum was
estimated to be 1.3-2.0 ng/g compared with control levels of 0.4-0.5 V.Q/Q. Levels of
dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, serotonin and
5-hydroxyindoleacetic acid were determined in discrete regions of the caudate-putamen.
Rats exposed for 60 and 165 days showed significantly increased levels of dopamine
and 3,4-dihydroxyphenylacetic acid, but these alterations were not seen in rats exposed
for 100 or 265 days. This suggests an increased synthesis and turnover of dopamine
that is reversible, even with continuous manganese exposure.
Lai et al. (1981 a) exposed female Wistar rats to 1 mg MnCI2»4H2O per mL
drinking water. Exposure was initiated at mating. Pups were exposed in utero, then by
maternal milk and, after weaning, by drinking water. The rats were exposed to
manganese either for 2 or for 24-28 months. The brains were dissected and then
analyzed. Levels of glutamic acid decarboxylase (GAD), choline acetyltransferase
(ChAT) and acetylcholinesterase (AChE) from treated rats were compared with the
concentrations of these enzymes in controls. GAD, ChAT and AChE are the
MANGANES.V V-11 02/24/93
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neurochemical markers for the GABA and cholinergic systems, which have also been
implicated in manganese toxicity (Sitaramayya et al., 1974; Bonilla, I978a,b). The effects
of chronic manganese exposure on the activities of GAD, ChAT and AChE were not
apparent in 2-month-old rats. Life-long exposure (over 2 years) to manganese produced
effects that tended to counteract age-related decreases in GAD, ChAT and AChE.
Leung et al. (1981) examined the same groups of rats and focused on monoamine
oxidase (MAO) activity. MAO is a key enzyme in brain amine metabolism. Leung et al.
(1981) reported that the only effect of manganese exposure on 2-month-old rats was a
small decrease in the neurotransmrtter amine, 5-hydroxytryptamine (5-HT) (serotonin) in
the cerebellum. No significant changes in the levels of dopamine appeared in young
rats. In rats 24-28 months old, no significant differences were found in
manganese-exposed rats as compared with controls.
In a related study, Lai et al. (1982a) examined male Wistar rats exposed to the
same drinking water regimen (1 mg MnCI2»4H2O/mL) for either 70-90 days or 100-120
days after birth. In addition, the rats had been exposed in utero. Levels of dopamine,
noradrenaline, serotonin and choline were determined. A significant decrease was seen
in the uptake of dopamine by synaptosomes isolated from the hypothalamus, striatum
and midbrain in 70- to 90-day-old rats, but not in the 100- to 120-day-old rats. This
finding agrees with Chandra and Shukla (1981). The study also found that choline levels
were significantly higher in 70- to 90-day-old exposed rats and significantly lower in
100- to 120-day-old exposed rats when compared with controls. The authors suggest
that this finding may be related to involvement of both the dopaminergic and cholinergic
systems in manganese toxicity. In rats exposed to the same regimen for_<_60 days (plus
MANGANES.V V-12 12/31/92
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in utero exposure), no effects were found in acetylcholinesterase activity in the brain (Lai
et al., 1982b). They conclude that, although the rat may not serve as an ideal model for
the neurotoxic effects of manganese, neurochemical effects are discernible when
analyses are made at the appropriate period (Lai et al., 1982a). The significance for
human exposure remains unclear.
Changes in the concentrations of dopamine and GABA were studied using mice
exposed to MnCI2 in the diet. Gianutsos and Murrary (1982) fed a 1% concentration of
MnCI2 in the diet to an unspecified number of male CD-1 mice for 1 month and then
raised the concentration to 4% for 5 additional months. Dopamine content in the
striatum and in the olfactory tubule at 6 months was reduced (p<0.05) compared with
controls. GABA content of the striatum was increased (p < 0.05) but neither the observed
increase in the substantia nigra area nor the decrease in the cerebellum reached
statistical significance. No changes in neurotransmitter levels were observed after only
1-2 months of exposure.
All et al. (1985) studied the effect of dietary protein on manganese neurotoxicity.
Rats received either a normal diet (21% casein) or a low protein diet (10% casein). Half
of each dietary group served as a control while the other half received MnCI2-4H2O (3
mg Mn/mL) in the drinking water for 90 days. The low protein diet resulted in decreased
levels of brain dopamine (DA), norepinephrine (NE) and 5-hydroxytryptamine (5-HT).
Manganese exposure resulted in a marked increase in DA and NE levels, which were
more pronounced in the low protein group. There was a significant decrease in 5-HT
levels because of manganese treatment, but only in the low protein group. Weaned F,
MANGANES.V V-13 02/24/93
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pups of treated rats exhibited the same effects. It was concluded that protein
undemutrition can increase vulnerability of rats to the neurotoxic effects of manganese.
Behavioral effects of chronic manganese exposure were studied by Nachtman et
al. (1986). Male Sprague-Dawley rats were administered 0 or 1 mg MnCI2»4H2O/mL in
drinking water for 65 weeks. The treatment did not result in any change in body weight.
The manganese-exposed rats did exhibit a significant increase in locomotor activity in
weeks 5-7 but at 8 weeks returned to control levels. Treated rats examined at 14 and
29 weeks were found to be more responsive to the effects of d-amphetamine (a loco-
motor stimulant that works primarily by releasing dopamine) than were controls. There
was no difference between groups at 41 or 65 weeks. The investigators concluded that
manganese exposure may result in a transient increase in dopaminergic function,
evidenced by increased spontaneous and d-amphetamine-stimulated locomotor activity.
In a behavioral study by Morganti et al. (1985), male Swiss mice (ICR strain) were
fed a powdered form of diet (Charles River's RMH 300) that contained 1 mg powdered
MnO2/g of diet. The authors stated that these mice consumed 5 g of food daily.
Sampling began after 16 weeks of feeding and continued at 2-week intervals for _<_30
weeks. Evaluated were open field and exploratory behavior, passive avoidance learning
and rotarod performance. Multivariate analysis of variance (2 treatments and 8 samples
by weeks of exposure) was used to test for intergroup differences. No significant
behavioral differences involving treatment appeared. This is in contrast to the inhalation
exposures 7 hours/day, 5 days/week for 16-32 weeks at levels >50 mg Mn/m3
(estimated to be comparable with the oral dose) for which significant effects related to
MANGANES.V V-14 02/24/93
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duration of exposure were found as well as significant uptake of manganese (Morganti
et al., 1985).
The only report of neurobehavioral toxicity in primates from orally administered
manganese is by Gupta et al. (1980). They administered 25 mg MnCI2«4H2O/kg (6.9
mg Mn/kg) orally to four male rhesus monkeys daily for 18 months. Animals were
maintained on monkey pellets, two bananas/day and tap water. The monkeys
developed muscular weakness and rigidity of the lower limbs. There were no
biochemical data. Histologic analysis compared with controls showed degenerated
neurons in the substantia nigra and scanty neuromelanin granules in some of the
pigmented ceils. This study is of limited use because only one dose level was studied.
Studies of the neurotoxic effects of excess manganese exposure are summarized
in Tables V-3 and V-4. Few studies have examined both behavioral and neurochemical
effects of oral exposure.
Digestive System Effects - Mitochondria-rich organs, such as the liver and
pancreas, are hypothesized to be most affected by excess manganese exposure.
Wasserman and Wasserman (1977) reported ultrastructural changes of the liver cells in
rats exposed to 200 ppm MnCI2 in their drinking water for 10 weeks. Increased
metabolic activity was inferred from an increased amount of rough endoplasmic
reticulum, the occurrence of multiple rough endoplasmic cisternae and prominent Golgi
apparatuses, and large Golgi vesicles filled with osmiophilic particles in the biliary area
MANGANES.V V-15 12/31/92
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TABLE V-3
Neurotonic Effects of MangantM
-------
TABLE V-4
Neurotonic Effects in Manganese in Experimental Animal*: Parenteral Studies'
Species
Rat
Rat
Rat
Rat
Rat
Rat
Rabbit
Monkey
Monkey
Monkey
Compound Route
NnCl,»4H,0 i.p.
MnCl,.4H,0 i.p.
MnCl,.4H|0 i.p.
MnCl,'4H,0 i.p.
MnCl,«4H,0 i.p.
NnClJ>4M^O i.p.
MnO, i . t .
MnO, i.m.
MnO, s.c.
MnO, s.c.
Dose (ng Mn/kg)
Single j Total
2.2
2.2
2.2
4.2
4.0
4.2
169.0
158,276*
36.1'
39.5'
79.0
158.0
535
401
268
189
120
63
169
434
72.2
355
711
1422
Duration
(months)
8
6
4
1.5
1
1
24
12
14
3
2
2
2
'Source: U.S. EPA, 1984
'Assumed body weight of rhesus monkey is 8.0 kg (U.S. EPA, 1980)
'Assumed body weight of squirrel monkey is 1.0 kg
"Body weight of monkey reported by authors to be 4.0 kg
NS • Not studied
Behavioral
NS
NS
CMS Abnormality
Histological Biochemical
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
Reference
Roussel and Renaud, 1977
Chandra and Srivastava, 1970
Sttarameyya et al., 1974
Shukla and Chandra, 1976
Chandra tt al., 1979b
Shukla and Chandra, 1976
Chandra, 1972
Pentschew et al., 1963
Neff et al., 1969
Suzuki et al., 1975
MANGANES.V
V-17
12/31/92
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of the Fiver cell. The authors suggested that the increased metabolic activity may be due
to biochemical processes related to the essentiality of manganese, in addition to the
maintenance of homeostasis of manganese during increased exposure. The authors
also suggested that other liver effects observed, such as the presence of
glycogenosomes in the biliary area, groups of collagen fibers in the Disse's spaces and
degenerative changes in some centrilobular liver cells may be direct toxic phenomena
or the consequence of the biologic effect exerted by manganese on other tissues.
Kimura et al. (1978) fed rats diets supplemented with 564 ppm of manganese as
MnCI2 for 3 weeks and found no significant difference in liver serotonin levels between
control and manganese-treated rats. In addition, MAO activity in the liver and
L-amino-acid decarboxylase activity in the liver remained unaltered. Structural changes
of the liver cells were not examined.
Shukla et al. (1978) administered 16 mg MnCl2«4H2O/kg bw in drinking water
(dose calculated by investigators) to rats for 30 days and reported significantly
decreased liver activity of succinic dehydrogenase and alcohol dehydrogenase
compared with controls. Significantly increased activities of MAO, adenosine
triphosphatase, arginase, glutamate-pyruvate transaminase, ribonuclease and
glucose-6-phosphatase were also reported in the liver of rats exposed to manganese
compared with controls. The level of a-amylase was significantly increased while the
level of 0-amylase was significantly decreased in the serum of exposed rats. Hietanen
et al. (1981) also studied the effect of manganese on hepatic and extrahepatic enzyme
activities. Male Wistar rats were exposed to 0.5% Mn (as MnCI2) in the drinking water
MANGANES.V V-18 12/31/92
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for 1, 4 or 6 weeks. Changes in several enzyme activities (e.g., arylhydrocarbon
hydroxylase, ethoxycoumarin 0-deethylase and epoxide hydrase) were observed at 1
week but not at 6 weeks. The activities were increased in the liver and decreased in the
intestines and kidney. Studies of the effects of excess manganese exposure on the liver
are summarized in Table V-5.
Hematologlc Effects - Decreased hemoglobin content has been reported in the
blood of 6-month-old anemic rabbits orally exposed to 2000 ppm Mn as MnSO4»H2O for
6 weeks, anemic newborn pigs orally exposed to 125 ppm Mn as MnSO4»H2O for 27
days (Matrone et al., 1959), and young, iron-deficient rats exposed for 32 weeks to
400-3550 ppm Mn as Mn3O4 (Carter et al., 1980). However, the hemoglobin depression
in baby pigs fed as much as 2000 ppm manganese was overcome by a dietary
supplement of 400 ppm iron (Matrone et al., 1959). Hartman et al. (1955) found that as
little as 45 ppm manganese provided in a milk diet to young lambs resulted in a
decrease in the concentrations of hemoglobin and serum iron. In a second experiment,
anemic lambs fed 1000 ppm manganese in the diet had depressed serum iron and
hemoglobin formation. It was determined that manganese interferes with iron absorption
rather than affecting hematopoiesis.
In a 13-week study, NTP (1992) administered diets containing 0, 1600, 3130,
6250, 12,500 or 25,000 ppm manganese suifate rnonohydraie to groups (10/sex/dose)
of F344 rats. Mean daily intake of manganese suifate monohydrate ranged from 98
mg/kg/day (32 mg Mn/kg/day) for the low-dose to 1669 mg/kg/day (542 mg
Mn/kg/day) for the high-dose males. For females, the range was 114 mg/kg/day (37
MANGANES.V V-19 12/31/92
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TABLE V 5
Liver Effects of Manganese Exposure in Animals'
Rat, male
Rat, Uistar, male
Rat, IIRC, male
Rat, ITRC, male
Rat, Uistar, male
Rat, Uistar, female
Rat, Sprague-Dawley,
male
Rat, ITRC, mate
Rat, ITRC, male
Monkey, rhesus
Route and Dose
drinking water
200 ppm MnCl,
drinking water
0.5*. Hn as MnCl,
gavage 10 mg/kg
MnCl,"iM,0 in 1
it* sal ine
drinking water 16
tng MnCl,»4H,0/kg
bu
diet 56A ppm Mn
,is HnCt,
dr inking water 1 ,
10 or 20 mg
MnCI,«
-------
Species, Strain, Sex
Monkey, squirrel
Monkey (Macaca
rouUata)
Route and Dose
s.c. ZOO mg MnO,
in 1 ml ot i ve of I
s.c. 0.25, 0.5 or
1.0 8 MnO, in
salin«
Duration
Z or 5
injection*
within 5
months
injection*
once a week
for 9 weeks
TABLE V-5 (cont.)
Converted Dose*
(•g Mn/kg
bM/injection)
Effects
126.4/injection*
39.5'
79
158
Variable, Mild cacuolar changes in
Uver cells
Irregular arrangement of hepatic cords
and lywphocytic infiltration
Reference
Neff et al., 1969
Suzuki et al., 1975
'Source: U.S. EPA, 1984
'The following default values have been used for dose conversion* (U.S. EPA, 1980)
Body Weight Water (I/day) Food (Fraction of body weight)
Rat 0.35 kg 0.049
Mouse 0.03 kg 0.0057
Monkey 8.0 kg
0.05
0.13
'Food consumption of 10X body w«ight (bw * 100 g) is u*ed
'Weight of squirrel monkey assumed to be 1.0 kg
"Weight of nonkey reported by authors to be 4.0 kg
NS > Not specified
MANGANES.V
V-21
12/31/92
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mg Mn/kg/day) for the low-dose group and 1911 mg/kg/day (621 mg Mn/kg/day) for
the high-dose group. No rats died during the study, and no clinical or histopathologic
findings were attributed to manganese exposure. Decreased body weight gain was
reported in males receiving >3130 ppm and females receiving >6250 ppm manganese
sulfate. Absolute and relative liver weights were decreased in males receiving >1600
ppm and females in the highest dose group only. Hematologic effects were also
reported: all groups of exposed males exhibited a significantly increased neutrophil
count; lymphocyte counts were decreased in males receiving >625Q ppm and females
in the three highest dose groups. Based on effects on iiver weight and neutrop'nii counts
in the male rats, the lowest dose of 1600 ppm (about 32 mg Mn/kg/day) is the LOAEL
for this study.
In a concurrent 13-week study, NTP (1992) administered diets containing 0, 3130,
6250, 12,500, 25,000 or 50,000 ppm manganese sulfats monohydrate to groups
(10/sex/dose) of B6C3F1 mice. Mean daily intake of manganese sulfate monohydrate
ranged from 328 mg/kg/day (107 mg Mn/kg/day) for the low-dose to 8450 mg/kg/day
(2746 mg Mn/kg/day) for the high-dose males. For females, the range was 390
mg kg/day (127 mg Mn/kg/day) for the low-dose group and 7760 mg/kg/day (2522
mg Mn kg/day) for the high-dose group. No deaths were attributed to manganese
exposure. All groups of male mice and female mice in the highest dose grcup exhibited
statistically significantly decreased body weight gain. Relative and absolute liver weights
were decreased in males in the highest dose group. Both sexes receiving 50,000 ppm
exhibited decreased hematocrit and hemoglobin concentration. The NTP report
suggests that these findings may indicate microcytic anemia, which may have resulted
MANGANES.V V-22 02/10/93
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from a sequestration or deficiency of iron. Males receiving £25,000 ppm also exhibited
significantly lower leukocyte counts; this finding was of questionable relevance to
manganese exposure. No clinical findings were reported to be attributed to manganese
exposure. The LOAEL for this study, based on significantly decreased body weight gan
in male mice, was 3130 ppm (about 107 mg Mn/kg/day).
In discussing trace metals and hemoglobin metabolism, Gamlca (1981) noted that
although exposure to divalent forms of manganese may cause a decrease in hemoglobin
levels, other chemical forms may not. This hypothesis does not explain the findings of
all of the above studies, since exposure to trivalent Mn3O4 decreased hemoglobin levels
in rats in the Carter et al. (1980) study and exposure to divalent MnCI2 produced
increased hemoglobin levels in rats in the Baxter et al. (1965) study. Conflicting results
of hematopoietic studies may more likely result from differences In the age and iron
status of the animal in addition to the route and duration of exposure. Carter et al.
(1980) found that as the rat matures, hematclogic and biologic values return to normal
because of a reduction in iron excretion and lowering of the rate of erythropofesis with
maturation. Matrone et al. (1959) found that depressed hemoglobin regeneration was
overcome by the addition of iron to the diet.
Cardiovascular System Effects - Kimuraetal. (1978) reported that rats exposed
to 564 ppm manganese in the diet showed significantly increased blood serotonin levels,
which resulted in decreased blood pressure.
MANGANES.V V-23 12/31/92
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Parenteral "=xposure.
Neurotoxic Effects - Intraperitoneal injection is not the most appropriate route
of administration for studies of >30 days, especially those whose purpose is to
investigate the neurotoxicity of chronically administered manganese. According to
Scheuhammer (1983), intraperitoneally administered manganese appears to have a
selectively toxic effect on the pancreas. This effect may then render any subsequent
changes found in the brain, especially subtle biochemical changes, difficult to interpret
since they may be secondary to cellular damage in the pancreas. The shortcomings of
the use of rodents and intraperitoneal administration render several studies of chronic
exposure to manganese and their reported CMS effects somewhat ambiguous.
Histopathologic evaluations of exposed rats by Chandra and Srivastava (1970), Chandra
et al. (1979b) and Shukla and Chandra (1976) found scattered neuronal degeneration
in the cerebral and cerebellar cortex. Daily intraperitoneal administration of 2-4 mg
Mn/kg for _< 120 days appeared to be the threshold for the appearance of microscopic
lesions. Their studies also demonstrated that a maximum number of degenerated
neurons is present when manganese concentration in the brain is at a maximum.
Two animal studies reported some of the characteristic histopathologic and
neurologic consequences of manganism found in exposed workers. Mustafa and
Chandra (1971) and Chandra (1972) reported paralysis of the hind limbs in rabbits
intratracheally inoculated with 169 mg Mn/kg bw (as MnO2). The paralysis developed
after a period of 18-24 months. In addition, the brains showed widespread neuronal loss
and neuronal degeneration in the cerebral cortex, caudate nucleus, putamen, substantia
MANGANES.V V-24 12/31/92
-------
nigra and cerebellar cortex, and a marked decrease in brain catecholamine levels and
related enzyme activity.
Primates are considered to be better models of the neurologic manifestations of
manganese intoxication than rodent species. Despite many deficiencies in experiments
(U.S. EPA, 1984), the studies have consistently reported extrapyramidaJ signs and
histologic lesions similar to those described in humans. Suzuki et al. (1975) exposed
monkeys subcutaneously to 39.5, 79.0 or 158.0 mg Mn/kg as MnO2 once a week for
9 weeks and found the latency of neurologic signs (tremors, excitability, choreiform
movement, loss of equilibrium, and contracture of hands) inversely related to cumulative
dose. Signs appeared earlier when higher doses were administered, but the severity of
symptoms was not totally dose-related. In an early study by Mella (1924), four rhesus
monkeys were treated with MnCI2 for 18 months while two monkeys served as controls.
The treated monkeys received intraperitoneal injections every other day with gradually
increasing doses of MnCL, starting at 5 mg and reaching a maximum of 25 mg per
injection. The monkeys developed choreic movements followed by rigidity, disturbances
of motility, fine hand tremors, and finally, contracture of the hands. Histologic changes
were reported in the putamen, the caudate, and the globus pallidus. Degenerative
processes were also found in the liver. Other studies of the neurotoxic effects of excess
manganese exposure are listed in Tables V-3 and V-4.
Digestive System Effects - Scheuhammer and Cherian (1983) reported adverse
effects in the pancreas resulting from intraperitoneally injected manganese. Toxic effects
included a pancreatitis-like reaction, which the authors suggest is potentiated by the
MANGANES.V V-25 12/31/92
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presence of manganese in the peritoneal cavity and thus would not occur as readily with
oral routes of exposure.
Pancreatic endocrine function is also affected by intraperitoneally injected
manganese. In conjunction with increased hepatic glycogenolysis and gluconeogenesis,
acute manganese exposure can affect carbohydrate metabolism in rats (Baly et al.,
1985). Manganese injection (40 mg/kg bw) resulted in a decrease in plasma insulin
levels, an increase in plasma glucose levels, and a transitory increase in glucagon
concentration.
The liver removes manganese by biliary excretion. Waassen (1974) reported that
>99% of an i.v. dose of manganese was excreted by rats in the feces. Large doses of
manganese, however, may result in cholestasis of the liver, similar to that seen in
humans exposed to manganese (Wrtzleben, 1969). One researcher (Waassen, 1974)
has suggested that both manganese and bilirubin are necessary for cholestasis to occur.
Table V-5 presents some of the liver effects of exposure to manganese observed in
animals.
Hematologic Effects - Animals injected with manganese have shown a variety
of hematologic and biochemical responses. Chandra et al. (I973b) reported decreased
serum alkaline phosphatase and inorganic phosphate and increased calcium levels in
rats exposed intratracheally to 400 mg of MnO2. The duration of exposure was not
reported.
MANGANES.V V-26 12/31/92
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Jonderko (1965) found increased serum calcium and decreased inorganic
phosphorous in rabbits exposed intramuscularly to 3.5 mg Mn/kg. These results agree
with those of Chandra et ai. (1973b). Details on the compound and the durwion of
exposure were not available.
Inhalation Exposure.
Neurotoxlc Effects - Studies of chronic inhalation exposure to manganous
manganese oxide (Mn3OJ (the major residue produced by combustion of MMT) report
no behaviorai or histoiogic CN5 abnormalities. Couiston and Griffin (1977) exposed
eight rhesus monkeys to 72 ng Mn/m3 (as Mr\3OJ for 12 months or to 3602 fig Mn/m3
(as Mn-jOJ for 23 weeks and observed no overt neurotoxic effects. Ulrich et al.
(1979a,b,c) observed no overt neurotoxic effects in rats and monkeys exposed to 11.6,
112.5 or 1152 ng Mn/m3 (as Mn3OJ for 9 months. The Couiston and Griffin (1977) and
Ulrich et al. (1979a,b,c) studies lack details of the clinica! examinations, lack biochemical
data and lack brain manganese data.
Neurologic and brain manganese measurements were made on rhesus monkeys
after inhalation exposure to MnO2. Bird et al. (1984) examined concentrations of
dopamine in the caudate, putamen, globus pallidus and substantia nigra of the brains
of four female rhesus monkeys exposed to 30 mg Mn/m3 for 2 years. Exposures were
for 6 hours/day, 5 days/week to dust <5 n diameter. No behavioral or abnormal
neurologic signs were noted, but dopamine concentrations in the caudate and globus
pallidus of treated animals were statistically significantly (p<0.01) decreased.
MANGANES.V V-27 12/31/92
-------
Manganese concentrations were 60-80% greater in the basal ganglia of the brain in the
treated animals.
Respiratory Pffects - The toxic effects of excess airborne manganese on the
lung include a primary inflammatory reaction, and at high exposure levels, a high
incidence of pneumonia. The severity of the effects increases when pathogens are
present, possibly because the manganese increases susceptibility to infection
(BergstrSm, 1977; Suzuki et al., 1978; Adkins et ah, 1980a,b,c). The effects of
manganese on the lung are reported to be the exclusive result of inhalation or
intratracheal exposure. The evidence from animal studies indicates a lack of gross toxic
effects at low levels of exposure; reversible respiratory symptoms have occurred in
humans exposed to airborne particulates that contained manganese (Nogawa et al.,
1973).
Hematopolellc Effects - In rabbits exposed to MnO2 by inhalation, Doi (1959)
found increased levels of hemoglobin, erythrocytes, leukocytes and lymphocytes.
Information on the duration and dose were not available.
Other Effects
Carcinogenicity. In a 2-year bioassay, groups of F344 rats (70/sex) were
administered 0,1500,5000 or 15,000 ppm manganese sulfate monohydrate (NTP, 1992).
These dietary concentrations were reported to be equivalent to an intake ranging from
91 mg/kg/day (30 mg Mn/kg/day) for low-dose males to 1019 mg/kg/day (331 mg
Mn/kg/day) for high-dose males. For females, the range of intakes was from 81
MANGANES.V V-28 12/31/92
-------
mg/kg/day (26 mg Mn/kg/day) for the low-dose group to 833 mg/kg/day (270 mg
Mn/kg/day) for the high-dose group. Interim sacrifices of 10 rats/group were made at
9 and 15 months. Survival of high-dose males was significantly decreased, starting at
week 93 of the study, because of advanced renal disease associated with manganese
exposure. Survival of females was not affected. Feed consumption was similar for all
groups, but by the end of the study, high-dose males exhibited a mean body weight that
was 10% lower than controls. No clinical findings or effects on hematologic or clinical
chemistry parameters were attributed to manganese exposure in any group. Tissue
concentrations of manganese were elevated in the livers of mid- and high-dose males
and females, concurrent with a decrease in hepatic iron concentrations. The only
pathologic finding was that of renal disease in high-dose males. No increases in any
tumor type reported were attributed to manganese exposure in rats.
In a 2-year bioassay, groups of B6C3F1 mice (70/sex) were administered 0,1500,
5000 or 15,000 ppm manganese sulfate monohydrate (NTP, 1992). These dietary
concentrations were reported to be equivalent to an intake ranging from 194 mg/kg/day
(63 mg Mn/kg/day) for low-dose males to 2222 mg/kg/day (722 rng Mn/kg/day) for
high-dose males. For females, the range of intake v/as from 238 mg/kg/day (77 mg
Mn/kg/day) for the low-dose group to 2785 mg/kg/day (905 mg Mn/kg/day) for the
high-dose group Interim sacrifices of 11 mice/group were made at 9 and 15 months.
No clinical findings or effects on survival were observed in any group of mice. Mean
body weights of males were not affected; however, female mice had a dose-related
decrease in mean body weight after week 37, The final mean body weights for the low-,
mid- and high-dose females were 6%, 9% and 13% lower than controls, respectively.
MANGANES.V V-29 02/10/93
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No differences were seen in feed consumption for any group. No effects were reported
on hematologic parameters. Tissue concentrations of manganese were significantly
elevated in the livers of all exposed females and in high-dose males. This was
associated with decreased hepatic iron.
Incidences of thyroid follicular cell hyperplasia were significantly greater in high-
dose males and females than in controls. The incidence of follicular cell adenomas was
0/50, 0/49, 0/51 and 3/50 (6%) for control, low-, mid- and high-dose males,
respectively. The historical control range for males was reported to be 0-4%. For
females, the incidence of follicular cell adenomas was 2/50, 1/50, 0/49 and 5/51 (10%)
for control, low-, mid- and high-dose groups, respectively. The historical control range
for females was reported to be 0-9%. None of the reported incidences were statistically
significantly increased over controls, nor were they dose-related in either sex. Also, the
follicular cell tumors were seen only at the termination of the study (729 days) and only
slightly increased relative to the historical control range in the highest dose groups. NTP
(1992) reported that the manganese intakes in the high-dose mice was 107 times higher
than the recommended dietary allowance. The relevance of these findings to human
carcmogenesis is questionable, particularly because of the very large intakes of
manganese required to elicit a response seen only at the end of the study, and at
frequencies not statistically significantly different from historical controls. NTP also
considers the marginal increase in thyroid adenomas of the mice to be equivocal
evidence of carcinogenicity.
MANGANES.V V-30 02/10/93
-------
Few other data are available on the carcinogenicity of manganese by the oraJ
route. Table V-6 presents those studies by other routes of exposure that have reported
a positive finding and provides the dose at which possible carcinogenic activity was
observed. DiPaolo (1964) subcutaneously or intraperitoneally injected DBA/1 mice with
0.1 mL of a 1% MnCI2 aqueous solution twice weekly for 6 months. A larger percentage
of the mice exposed subcutaneously (67%) and intraperitoneally (41%) to manganese
developed lymphosarcomas compared with controls injected with water (24%). In
addition, tumors appeared earlier in the exposed groups than in the control groups. The
number of tumors other than lymphosarcomas (e.g., mammary adenocarcinomas,
leukemias, injection site tumors), however, did not differ significantly between the
exposed and control groups. A thorough evaluation of the results of this study was not
possible because the results were published in abstract form and lacked sufficient detail.
Stoner et al. (1976) exposed Strain A/Strong mice of both sexes, 6-8 weeks old,
intraperitoneally to 6, 15 or 30 mg MnSO4/kg bw 3 times a week for a total of 22
injections. The total administered doses were 132, 330 and 660 mg MnSO4/kg bw. The
frequency of lung tumors in exposed mice was compared with that in controls. Table
V-7 presents the results of the study, which showed that a slight but statistically
significant increase in the number of pulmonary adenomas per mouse was associated
with administration of the highest dose (660 mg MnSO., kg). Although the response was
somewhat elevated at the other doses, it was not statistically significant. The study
results are suggestive of carcinogenic activity but do not conclusively meet specific
criteria for the interpretation of lung tumor data in this mouse strain as a positive
response (Shimken and Stoner, 1975).
MANGANES.V V-31 02/10/93
-------
TABLE V-6
'.L»niL.ir y ot Care tnogemctty Studies Reporting Positive findings for Selected Manganese Compounds'
Results
*1X • Lymphosarcomas
67X • Lymphosarcomas
24X - LymphosarcoMS
67X • Lung adfenomas
31-37X - Lung adenomas
tOX (males) • MbrosarcaM»
24X (females) - Fibrosarcom*
4X (males and females - Fibrosarcomas
Compound Spoc 10-,
Manganese chloride inou^e
ITKJU'.t*
Manganese sulfate mouse
Manganese rat
acelylacetonale (MAA)
Route Dose
i .p. 0.1 rnt of IX
s.c . 0.1 nt of IX
OX (control)
i.p. 660 ing/kg
0 mg/kg
i .m. 1200 mg/kg"
0 mg/kg
Duration
(weeks intermittent)
26
26
8
26
'Source: U.S. EPA, 198A
"As reported in NIOSH, 1984
Reference
DiPaolo, 1964
Stoner et al.. 1976
furst, 1978
MANGANES.V
V-32
02/10/93
-------
TABLE V-7
Pulmonary Tumors in Strain A Mice Treated with Manganese Sulfate*
Group 1
Untreated control
Solvent control
(0.85X Nad)
Treated
Treated
Treated
20 ng uretharve*
Total Dose
mg MnSO./kg |
0
0
1J2
330
660
0
mg Mn/kg
0
0
42.9
107.2
214.4
0
Mortality
1/20
1/20
1/20
0/20
2/20
2/20
Mice with Lung
Tumors (X)
6/19 (31)
7/19 (37)
7/19 (37)
7/20 (35)
12/18 (67)
18/10 (100)
Average Number
Tumors/Mouse*
0.28+0.07
0.42+0.10
0.47+0.11
0.65+0.15
1.20+0.49
21.6+.2.81
Value'
NA
NA
NS
NS
0.05*
NR
"Source: Stoner et al., 1976
•x+S.E.
'Student t-test
"Fisher Exact Test p = 0.06s
"Single intraperitoncal injection
NA » Not applicable; NS * not significant; NR • not reported
MANGANES.V
V-33
12/31/92
-------
Furst (1978) exposed F344 rats intramuscularly or by gavage to manganese
powder, MnO2 and manganese (II) acetylacetonate (MAA). Swiss mice were exposed
intramuscularly to manganese powder and MnO2. Table V-8 presents the results of the
study, which showed a statistically significant number of fibrcsarcornas at the injection
site in maie (40%) and female (24%) rats exposed intramuscularly to MAA compared with
controls (4% male, 4% female). No difference in tumor incidence was found between
rats and mice exposed to manganese powder and MnO2 and controls. The U.S. EPA
(1984) noted that the study results regarding MAA, an organic manganese compound,
cannot necessarily be extrapolated to pure manganese or inorganic manganese
compounds.
Sunderman et al. (1974, 1976) exposed Fischer rats to 0.5-4.4 mg manganese
dust intramuscularly and found that no tumors were induced at the injection site.
Subsequent studies by Sunderman et al. (1980) suggest that manganese dust may even
inhibit local tumor induction.
Witschi ei ai. (1981) exposed female A/J mice intraperitoneaiiy to 80 mg/kg MMT
and found that although cell proliferation was produced in the lungs, lung tumor
incidence did not increase.
Mutagenicity. The available information supports a positive mutagenic role for
manganese. The bone marrow cells of rats given manganese orally (as MnCy at
50 mg/kg showed an unusual incidence of chromosome aberrations (30.9%) compared
with those of control animals (8.5%) (Mandzgaladze, 1966; Mandzgaladze and
MANGANES.V V-34 12/31/92
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TABLE V-8
Carcinogenicity of Manganese Powder, Manganese Dioxide end Manganese Acetylacetonate in fVA Rats and Sulit Albino Mlct"
CoBpound*
Triglyceride control
Manganese powder
Manganese acetylacetonate
Trfglyceride control
Manganese dioxide
Triglyceride control
Manganese powder
Triglyceride control
Manganese powder
Triglyceride control
Manganese dioxide
Manganese dioxide
Species Route Treatment Schedule'
rat f.M. 0.2 tl/MOnth x 12 Months
rat i.«. 10 BB/Bonth x 9 Month*
rat i.H. SO Bg/Booth x 6 months
rat i.M. 0.2 ML/Bonth x 12 aonths
rat i.B. 10 mg/Booth x 9 Months
rat oral 0.5 at, tulc« BoothIy x 12 Booths
rat oral 10 Bg, tuice BoothIy x 12 Booths
mouse i.M. 0.2 BL/injection x 3 injections
mouse i.M. 10 ag (single injection)
Mouse i.M. 0.2 at/Injection x 12 injection*'
mouse i.M. 3 Mg/inject1on x 6 injections'
mouse i.M. 5 Mg/injection x 6 injections'
Total Dose
Tuaor Type
Incidence
Male* FeMles
2.4 rt.
90 MQ
300 BB
2.4 ML
90 Bg
12.5 ML
240 MO
0.6 ML
10 Mg
24 at
15 W
30 BO
LynphoBas/leuke»ia
FibrosarccsM*4
LyMphoBt*/ 1 eukeait a
FibrosarccsM*
Lymph OBM/ I eukeai a
f ibrosarcoBts
Lywphoaas/ 1 eukeB i a
FibrosarccsM*
LywphoBM/ 1 eukerni a
FibroaarcoMa*
LyMpnoBas/ leukemia
FibrosarcomM
Lymph onas/ 1 eukeai a
FibrosarcoM*
Leutenfa
Lynphooas
LeukaMia
LyBphoaas
LeukaMia
LyvphoBM
Leukaaiia
Lymph onas
LeukeBia
LywphoBas
1/25
1/25
3/25
3/25
2/25
10/25*
0/25
0/25
0/25
0/25
3/25
0/25
0/25
0/25
NT
NT
MT
MT
NT
NT
NT
NT
NT
NT
3/25
1/25
5/25
0/25
2/25
6/25
V25
0/25
3/25
0/25
3/25
0/25
0/25
0/25
2/25
1/25
6/25
1/25
2/25
0/25
4/25
1/25
1/25
2/25
'Source: Furat, 1978
'Compounds suspended in 0.2 ML (i.M.) or 0.05 ML (gavage) trlctanoln
'Duration of expertBtnts was not stated, but was laplied to be 2 years In the rat studies. The average Mights of the treated and control alee ranged
froM 22-25 g at the start of the experiawnts to 33-39 g at the and of the experiments.
'Injection site fibrosarcoma
'Fischer Exact Test p « 0.002
'Fischer Exact Test p • 0.049
'Incidence includes rhabomyosarconas and 1 ByxosarcoM
'Intervals between injections not stated
NT • Not tested
MANGANES.V
V-35
12/31/92
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Vasakidze, 1966). Manganese dichloride has been reported to be mutagenic (or
Escherichia coli (Demerec et al., 1951; Durham and Wyss, 1957) and Serretia
marcescens (Kaplan, 1962). Manganese oxide (Mn3O4) was not mutagenic in
Salmonella typhimurium or Saccharomyces cerevisiae (Simmon and Ligon, 1977).
Manganese sulfate monohydrate was not mutagenic in S. typhimurium strains TA97,
TA98, TA100, TA1535 or TA1537, either with or without exogenous metabolic (S9)
activation (NTP, 1992).
The manganese ion (Mn2+) has been shown to bind with DNA and chromosomes
(Kennedy and Bryant, 1986; Yamaguchi et al., 1986). In cultured mammalian cells, both
MnCI2 and KMnO4 produced chromosome aberrations, including breaks, exchanges and
fragments (Umeda and Nishimura, 1979). True DNA-strand breaks have also been
induced by manganese in Chinese hamster ovary cells and human diploid fibroblasts
(Hamilton-Koch et al., 1986; Snyder, 1988). Tests for induction of sister chromatid
exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells were
positive for manganese sulfate monohydrate in the absence of S9 metabolic activation;
in the presence of S9, only the sister chromatid exchange test was positive (NTP, 1992)
Manganese sulfate monohydrate did not induce sex-linked recessive letna'
mutations in germ cells of male Drosophila melanogaster (NTP, 1992) A study by
JoardarandSharma (1990) demonstrated that both MnSO4and KMnO4weredastogenic
in mice following oral administration for 3 weeks, with MnS04 being more potent. The
frequencies of chromosomal aberrations in bone marrow cells and micronuciei were
MANGANES.V V-36 02/10/93
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significantly increased by both salts. There was also an enhancement of sperm-head
abnormalities which demonstrated a statistically significant dose-response trend.
Reproductive Effects. Gray and Laskey (1980) exposed male mice to 1100 ppm
Mn as Mn3O4 in a casein diet from gestation day 15 to 90 days of age. Sexual
development was retarded as indicated by decreased weight of testes, seminal vesicles
and preputial glands. Reproductive performance was not evaluated.
Laskey et al. (1982) found a dose-related decrease in serum testosterone
concentration (without a concomitant increase in serum lutinizing hormone
concentration) and reduced fertility at the highest dose in rats exposed to 0, 400, 1100
or 3550 ppm Mn (as Mn3OJ orally in the diet from day 2 of mother's gestation to 224
days of age. Testes weight as well as litter size, number of emulations, resorption and
preimplantation deaths and fetal weights were not affected.
Laskey et al. (1985) conducted studies to assess the effect of manganese on
hypothalmic, pituitary and testicular functions. Long-Evans rat pups (8/lltter) were dosed
by gavage from day 1 to day 21 with a 50% sucrose solution containing paniculate
Mn3O4. The actual dose of manganese was calculated to be 0, 71 or 214 mg Mn/kg
bw/day. Effects attributed to manganese included slight decreases in body and testes
weights and a reduction in serum testosterone. There was no indication of hypothalmic
or pituitary malfunction, and it was suggested that the decrease in testosterone was due
to manganese-induced damage of testicular Leydig cells.
MANGANES.V V-37 12/31/92
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A series of studies by Chandra and colleagues have consistently reported
degenerative changes in the seminiferous tubules in the testes after parenteral exposure
to manganese (Chandra, 1971; Shukla and Chandra, 1977; Imam and Chandra, 1975;
Chandra et al., 1973a, 1975). The U.S. EPA (1984) notes that results from parenteral
studies are of limited value in predicting the reproductive hazards of ingested
manganese. Table V-9 summarizes studies of the reported reproductive effects of
exposure to manganese.
Teratogenicity. In animals, manganese deficiency during pregnancy causes a
variety of developmental defects related to impaired mucopolysaccharide formation.
Resultant defects indude impaired coordination, which was due to defective bone otolith
calcification and growth deficiencies, reproductive difficulties and CNS changes (Oberleas
and Caldwell, 1981; Hurley, 1981). The effect of manganese excess has been studied
by only a few investigators.
The embryotoxic and teratogenic potential of manganese during organogenesis
was investigated by Sanchez et al. (1993; abstract only). Pregnant Swiss mice were
administered daily subcutaneous injections of 0, 2, 4, 8 or 16 mg/kg of MnCI24H2O on
days 6-15 of gestation, and dams were sacrificed on gestational day 18. Significant
reductions in weight gain and food consumption were reported in dams receiving >8
mg/kg, and treatment-related deaths were reported at 16 mg/kg. A significant increase
in the number of late resorptions was observed at doses >4 mg/kg, and reduced fetal
body weight and an increased incidence of morphological defects were reported at >8
MANGANES.V V-38 04/09/93
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TABLE V-9
Reproductive Effects of Exposure to Manganese
Compound Species
Mn,0.
Mn,0.
Mn,0.
MnCl,
MnCl,'4H,0
MnCl,'4H,0
MnSO.
MnO,
rat
rat
rat
rat
rabbit
rat
rabbi t
Route | Dose
oral 1100 ppm Mn
oral 400 ppra Mn
1100
3550
oral 71 MQ Mn/kg
(gdvage) 214
i.p. 8 mg/kg daily
i.p. 15 mg/kg daily
3.5 ng/kg
i.p. 6 mq Mn/kg
i.t. 250 tog/kg single dose
Effect
Decreased weight of tcstes, seminal vesicles and
preputial glands after 90 days.
Dose-related decrease in serum testosterone
concentration. Reduced fertility at 3550 pen
after 224 days.
Decreased body and testes weights. Reduction in
serum testosterone.
Degenerative changes in -50X of seminiferous
tubules after 150 and 160 days.
Increased Mn in testes; decreased nonprotein
sulfhydryls and decreased activity of glucose-6-
phosphate dehydrogenase and glutathione reductase
after 15-45 days.
Inhibition of soccinic dehydrogenase in
seminiferous tubules after 5 days. Morphologic
changes were not apparent.
Increased Mn in testes after 25-30 days.
Degenerative changes in 105t of seniniferous
tubules.
Destruction and calcification of the seminiferous
tubules at 8 months. Infertile females.
Reference
Gray and Laskey, 1980
Laskey et al., 1982
Laskey et al., 1985
Chandra, 1971
Shukla and Chandra, 1977
1mm and Chandra, 1975
Chandra et al., 1975
Chandra et al., 1973a
MANGANES.V
V-39
02/10/93
-------
mg/kg. No difference was seen in the incidence of individual or total malformations in
treated groups compared with controls.
Excess manganese during pregnancy has been shown to affect behavioral
parameters in rodents. Lown et al. (1984) studied behavioral effects in mice of in utero
and lactational exposure to airborne MnO2 dust. Preconception exposure was to
49.1jf.2.3 mg Mn/m3 for 12 weeks (7 hours/day, 5 days/week) and to 85.3.+.15.6 mg
Mn/m3 for 4 additional weeks. All females were exposed preconceptually and randomly
assigned to MnO2 or control until day 17 of gestation. Pups were fostered equally
among exposed and nonexposed mothers. Treatment effects on growth and behavior
of offspring were evaluated by multivariate analysis of variance. Prenatal exposure
resulted in significantly reduced weight at day 45 and higher mean number of pups.
Measures of neonatal gross locomotor activity, maternal retrieval latency and day 45
offspring behavior showed effects on postnatal development. Prenatal exposure resulted
in significantly reduced activity scores. Exposures both in utero and by suckling
depressed adult rearing frequency, exploratory behavior and general activity.
There are other supporting reports of effects of manganese on learning in the
adult rat (Murthy et al., 1981), and by a study of the distribution of ^Mn in fetal, young
and adult rats (Kaur et al., 1980). Kaur et al. (1980) found that younger neonates and
19-day fetuses were more susceptible to manganese toxicity than the older groups.
Manganese was localized to the liver and brain in the younger groups and there was
more manganese per unit of weight in the younger animals compared with the older
groups (Kaur et al., 1980). No fetal abnormalities were seen when 18-day embryos were
MANGANES.V V-40 04/09/93
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exposed to 16 /imol/200 g maternal weight, but this is a late stage for detecting
morphologic defects.
Kontur and Fechter (1985) exposed pregnant Long-Evans rats to 0, 5, 10 or 20
mg/mL of MnCI2 in drinking water throughout the gestational period. Rats in the 10 and
20 mg/mL groups had a reduced water intake and a significant decrease in weight gain.
There was also a significant decrease in birth weight in the 20 mg/mL group. At 1 day
of age, pups from the 5 and 10 mg/mL group were found to have significantly increased
manganese levels in the forebrain, which was no greater in the 10 mg/mL group than
in the 5 mg/mL group. The increased manganese levels were not associated with any
changes in catecholamine function, nor was there any effect on startle responses in the
exposed pups. It was concluded that prenatal exposure to manganese is not toxic to
developing rats, probably because of limited placental transfer.
JSrvinen and AhlstrSm (1975) exposed female rats to 4, 24, 54,154,504 or 1004
mg Mn/kg (as MnSO4»7H2O) in the diet for 8 weeks after weaning and during
pregnancy. No maternal reproductive or fetal teratogenic effects were found. At the
higher manganese levels (>154 mg Mn/kg bw) an increase in whole body content of
manganese in fetuses and in the livers of dams was reported. However, no increase in
liver manganese was found in nonpregnant females.
Laskey et al. (1982) found a dose-related decrease in serum testosterone
concentration (without a concomitant increase in serum LH concentration) in the male
offspring of treated dams. Female rats exposed to 0, 400, 1100 or 3550 ppm Mn (as
MANGANES.V V-41 04/09/93
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Mn-O4; 50 ppm as MnSOJ orally in the diet from day 2 of gestation to 224 days of age
exhibited reduced fertility at the highest dose. Tsstss weight of the offspring as well as
litter size, number of ovuiations, resorptions and preimpiantation deaths and fetal weights
were not affected.
Summary
LD.Q values for soluble manganese compounds range from an average of 102 mg
Mn/kg for pa'entera! exposure to 583 rng Mn/kg for era! exposure with the highest
toxicfty occurring in oldest and youngest rats (Kostiai et al., 1978). The CNS is the
primary system affected by chronic manganese exposure in humans. No accurate
dose-response relationship for neurologic effects by inhalation exists at this time. Oral
animal exposures are difficult to interpret because laboratory rodents ingesting
manganese in food and water do not exhibit the neurobehavioral deficits (muscular
rigidity, tremor and paralysis) found in humans, and the one study of ingestion In
primates used only one dose. Alterations in neurcchemicai parameters have been used
instead as indicators of CNS effects in animals. Primates appear to be a better model
of adverse CNS effects arising from excess manganese exposure.
The intraperitoneal administration of manganese to animals has also been
questioned in studies designed to detect the chronic neurotoxic effects of manganese
exposure. Scheuhammer (1S83) reported that intraperiioneaiiy administered manganese
exerts a selectively toxic effect on the pancreas that may render subsequent
neurochemicai changes difficult to interpret.
MANGANES.V V-42 04/09/93
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Toxic effects of chronic manganese exposure are also seen in the pulmonary,
hematopoietic, cardiovascular, reproductive and digestive systems. Pulmonary system
effects are limited to inhalation exposure and are reported to be insignificant at low levels
(U.S. EPA, 1984). Hematologic and biochemical effects vary depending on age and iron
status. Young and irondeficient animals are more likely to exhibit hematotogic and
biochemical effects (Carter et al., 1980). A single study of cardiovascular effects in
animals reported a significant increase in blood serotonin levels and a decrease in blood
pressure (Kimura et al., 1978). Although animal studies of the Gl effects of manganese
exposure are not conclusive, studies of liver function and structure are generally
adequate. Large doses of manganese may produce cholestasis in animals, similar to
that seen in humans (U.S. EPA, 1984).
The organs with greatest sensitivity to manganese include the brain, lung, fiver
and endocrine glands. Parenteral, as opposed to oral, exposure to manganese may
result in more selective and toxic organ effects, especially those observed in the
pancreas (Scheuhammer, 1983).
The U.S. EPA (1984) reports that the data from available studies of the
carcinogenic effects of manganese are inadequate for animals and lacking for humans.
Thus, the weight-of-evidence for manganese carcinogenicity would currently be rated as
Group D (not classified) using the guidelines for carcinogen risk assessment of the U.S.
EPA (1986a). This category denotes that more information is needed to reach a
definitive conclusion. Testing is underway by the National Toxicology Program to
address the carcinogenicity of orally administered manganese sulfate in rats and mice.
MANGANES.V V-43 04/09/93
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Reproductive studies present histologic and biochemical evidence of toxicity to
reproductive organs (Chandra et al., 1973a, 1975; Gray and Laskey, 1980; Laskey et al.,
1982). The U.S. EPA (1984) has questioned the value of using parenteral studies in
predicting the reproductive hazards of ingested manganese.
The teratogenic effects of excess manganese exposure during pregnancy may
include altered behavioral parameters in offspring, but the evidence at this time is
insufficient to define manganese as teratogenic (Lown et al., 1984).
MANGANES.V V-44 04/09/93
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VI. HEALTH EFFECTS IN HUMANS
Introduction
Most of the information on the toxicity of manganese in humans is derived from
the inhalation of large amounts of manganese oxides by occupationally exposed groups.
Although the pulmonary effects of manganese inhalation are not relevant to the ingestion
of manganese, other systemic effects are. Table VI-1 summarizes some of the studies
of manganese health effects in humans and exposure-response relationships. The
psychologic and neurologic effects of manganese exposure upon the CNS, collectively
referred to as manganism, have been the primary focus of these studies. The syndrome
is described in the next section, Clinical Case Studies. For years manganism has been
considered a model of Parkinson's disease, but Barbeau (1984) suggested that it is
better characterized as a mixture of bradykinesia and dystonia.
The U.S. EPA (1984) reported that >550 cases of manganism have been
recorded in the literature since the first report by Couper (1837). Case reports have
consistently reported that human manganese exposure produces signs and symptoms
of neurotoxicity, which include both psychologic disturbances and neurologic disorders;
the latter especially seem irreversible (U.S. EPA, 1984). Although the neurotoxic effects
of manganese exposure can erupt after only a few months, the latency typically is 2-3
years or longer.
CJinical Case Studies
Most of the studies, particularly the older ones, concentrate on clinical
descriptions (case reports or clinical studies) rather than rates of response for a given
MANGANES.VI VI-1 02/11/93
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TABLE VI-1
Studies of Kanganlsai In Ifiaens and Exposure-Response Relationship*
Source of Inhalation Che*
Expocurt (particl
ical Exposure Laval Duration of
a size) (*g Hn/af Expoaure (range)
Ore crushing oxides, mostly HnO, 10-30 3.3 veer average
mitt/dust (MR) 30-180
Manganese nine M
Manganese nine; NR (90S <5
dusts
62.5-250 178 days
M) 25-450 -1 amth to 10
years
Manganese nine oxides (NR) 1.5-16' 8.2 ytar average
Industrial plants NR
<5 m
5-30
Dry-cell battery 65X HnO, (NR) 6.8-42.2* 7.5 ytar average
industry; dusts (1-16 years, casea)
Ferromanganese ferromaoganese, 2.1-12.9 and/or 6-26 years In five
production and small amounts of 0.12-13.3 cases
processing MnO, Hn.O. (95X <5 20 years
Nuaber Affected/
Muaber Studied
0/9
11/25
12/72
Nt
IS/83
(9 awnths to 16
yeara)
0/38
7/117
8/36
5/71
26/160
40/100
62/369
Signs and
SyaptoM'
None
UXsMvanlsai
•anginlta
150 cases
avnganfM
•anganla*
none
6X swnganlaai
22. 2X awnganisa
peycfioais
7X avnganlsai
3m subjective
syaptoav; 2X
•health disorders
due to
sMneanfsaV;
SVtptOM
increased with
nuaber of years
of aaployaient
40X subjective
svaptojBs; 8-10X
single neurologic
signs, e.g.,
tremor of fingers
16.8X slight
neurologic signs,
e.g., tremor at
Reference
Film et al.,
1941
Amola et al.,
19Ua.b
Rodier, 1955
Scholar et al.,
1957
Tanaka and
Lieben, 1969
Eswra et al.,
1971
Saiyth et al.,
1973
Suzuki et al.,
1973a
Suzuki et al.,
1973s
Sarlc et al.,
1977
rest, pathologic
reflexes
MANGANES.VI
VI-2
12/10/92
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Source of Inhalation
Exposure
Control I elctrode
plant
Control II aluminum
rolling nil I
(art)lent levels)
Welding fLines
Chemical
(particle size)
NR
Manganese salts and Mn dust
oxides plants
Exposure Level
(•g Mn/sf
0.002-0.03
(emissions
frosj
ferraaanganese
plant)
<0.07
0.44-0.99*
0.5-0.8*
0.88-2.6*
0.07-8.61'
(•edian 0.97)
control
TABLE VI-1 (cont.)
Duration of Exposure
(range)
Ml
NR
20.2 (Bean year) (10-31)
21.9 (Bean year) (2-32)
U.I (Bean year) (6-27)
7.1
0
(1-19)
Number Affected/
MuAer Studied
11/190
0/204
5/20
10/20
9/20
MR/H1
NR/140
Signs and Syaptoaw* Reference
5.8X neurologic
findings
none
25X slight neurologic
signs (brisk deep
reflexes)
SOX
45X
Exposed perforsMd
•less well" in
psychoaotor tests
'Source: U.S. EPA (1984)
*Percentage is given if taaple hat been selected such that the rate can be considered an estimate of prevalence.
'Range of averages for different areas or workstat ions saspled
'in worker's breathing zone
'Personal samplers
NR * Not reported
Saric at al.,
1977
Saric et al.,
1977
Chandra
et al., 1981b
Roels et al.,
1987s
MANGANES.VI
VI-3
12/10/92
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exposure (epidemiologic studies). Kilburn (1987) has published a report on the possible
role of manganese in the neurologic disorders found to occur in the isolated Aboriginal
population of Groote Eylandt, a large island off the northern coast of Australia. This area
is rich in manganese deposits. Although it is difficult to determine actual levels of
manganese exposure, elevated levels found universally in the hair of the Aborigines is
testament to increased exposure. Elevated whole blood manganese has also been
reported in a few individuals. The small population of Groote Eylandt and problems in
defining an appropriate control group have made a statistical analysis of clinical
problems impossible. However, high levels of stillbirths and congenital malformations
have been revealed, and an association with manganese is implicated. A study of the
neurologic status of the Aborigines has found two general syndromes: one
characterized by amyotrophy and weakness and the other by ataxia and oculomotor
disturbances. While this study is still in progress, the role of manganese in these
neurologic deficits cannot be clearly defined but must be considered as a possible
cause.
A case report by Yamada et al. (1986) published the findings of an autopsy
performed on a patient who had worked for 12 years in a manganese ore crushing plant.
Two years after he began work, he developed difficulty in walking and diminished libido.
Years later, neuropsychiatnc symptoms developed, including euphoria, emotional
incontinence, masked face, monotonous speech, "cock walk," weakness of extremities,
tremor of the eyelids, and exaggeration of knee jerks. Autopsy revealed that the major
neuropathologic change was degeneration of the basal ganglia with severe affliction of
MANGANES.VI VI-4 02/11/93
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Cook et al. (1974) described symptoms and signs of chronic manganese
intoxication in six American workers in a manganese ore crushing plant. Symptoms
included somnolence, gait imbalance, slurred speech and impaired fine movements,
consistent with other descriptions in the literature. However, none of these individuals
demonstrated "manganese psychosis" before onset of these symptoms as had miners
in other studies. Signs included bradykinesia, postural instability, impaired arising ability,
masked faces and speech disorder. One patient did not exhibit major symptoms until
3 years after cessation of exposure.
Kawamura et al. (1941) reported on health effects resulting from the ingestion of
manganese-contaminated well water by 25 individuals. The well water had been
contaminated with manganese dissolved from dry cell batteries buried near the well. The
length of exposure to manganese was estimated to be 2-3 months. The concentration
of manganese in the well water was analyzed 7 weeks after the first case appeared and
was determined at that time to be -14 mg Mn/L (as Mn3O4). However, when re-
analyzed 1 month later, the levels were decreased by about half. Therefore, the actual
exposure was probably to drinking water containing 28 mg Mn/L or higher. Assuming
a daily water intake of 2 L, and an additional manganese intake from food of at least 2
mg, day, this represents a dose of at least 58 mg Mn/day. This intake cf manganese
is about 10-20 times the level considered to be safe and adequate by the Food and
Nutrition Board of the National Research Council (NRC, 1989). Health effects included
lethargy, increased muscle tonus, tremor and mental disturbances. The elderly were
more frequently affected; children were affected less. Three deaths occurred, one from
suicide. Upon autopsy, the concentration of manganese in the brain of one case was
MANGANES.VI VI-5 02/16/93
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found to be 2-3 times higher than in two controls. In the brain, extreme macroscopic and
microscopic changes were seen, especially in the globus pallidus. The authors also
reported excess zinc in the well water, but concluded that the zinc appeared to have no
relation to symptoms produced and pathologic changes found in the tissues. This
conclusion was based upon the fact that, upon autopsy, morphologic changes were
observed in the corpus striatum, which is characteristic of manganese poisoning, but not
of zinc poisoning. While manganese appears to be the cause of toxicity in these
individuals, several aspects of this outbreak are inconsistent with traits of manganism in
humans resulting from inhalation exposure. First, the symptoms appeared to come on
very quickly; for example, two adults who came to tend the members of one family
developed symptoms within 2-3 weeks. Also, the course of the disease was very rapid,
progressing in one case from initial symptoms to death in 3 days. Those who did
survive recovered from the symptoms, even before the manganese content of the well
had decreased significantly after removal of the batteries. This is in contrast to the
longer latency period and irreversible damage caused by inhalation exposure to
manganese. These differences may represent differences in the pharmacokinetics of
ingested vs. inhaled manganese, but there is little information to support this Therefore.
wh;ie there is no question that these individuals were exposed to high !eve:s c'
manganese, it is not clear that the observed effects were due to manganese a!cne
Individual case reports have focused on acute exposure to manganese that.
although rare, has been found to occur following accidental or intentional mgesticn of
large amounts of manganese as potassium permanganate. Oral ingestion of 300 mg of
potassium permanganate was reported to result in extensive damage to the distal
MANGANES.VI VI-6 02/16/93
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stomach and pyloric stenosis in a case described by Dagli et al. (1973). Two cases of
methemoglobinemia were reported following ingestion of an unspecified amount of
potassium permanganate, which had been prescribed by African witch doctors
(Mahomedy et al., 1975). The lowest dose of potassium permanganate found to
produce toxic effects in a human was 2400 jig/kg bw/day orally ingested by a woman.
This information, as reported in a 1933 French study cited in NIOSH (1984), was not
available for review.
Additional case studies have also pointed to the potential for manganese
poisoning, but are difficult to assess quantitatively. One involved a 59-year-old male who
was admitted to the hospital with symptoms of classical manganese poisoning, including
dementia and a generalized extrapyramidal syndrome (Banta and Markesbery, 1977).
The patient's serum, hair, urine, feces, and brain were found to have manganese
"elevated beyond toxic levels," perhaps a result of his consumption of "large doses of
vitamins and minerals for 4 to 5 years." Unfortunately, no quantitative data were
reported.
Another case study of manganese intoxication involved a 62-year-old male who
had been receiving total parenteral nutrition that provided 2.2 mg of manganese (form
not stated) daily for 23 months (Ejima et al., 1992). The patient's whole blood
manganese was found to be elevated, and he was diagnosed as having parkinsonism,
with dysarthria, mild rigidity, hypokinesia with masked face, a halting gait, and severely
impaired postural reflexes. Assuming an average absorption of roughly 5% of an oral
MANGANES.VI VI-7 08/09/93
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dose, the i.v. dose of 2.2 mg Mn/day would be approximately equivalent to an oral intake
of 40 mg Mn/day.
Epidemioloalc Studies
There was one epidemiologic study of manganese in drinking water performed by
Kondakis et aK (1989). Three areas in northwest Greece were chosen for this study,
with manganese concentrations of 3.6-14.6 jig/L in area A, 81.6-252.6 \ig/L in area B,
and 1800-2300 ng/L in area C. The total population in the three areas being studied
ranged from 3200 to 4350 people. The study included only individuals over the age of
50 drawn from a random sample of 10% of all households (n=62, 49 and 77 for areas
A, B and C). The authors reported that "all areas were similar with respect to social and
dietary characteristics,' but few details were reported. The investigator subsequently
estimated a dietary intake of 5-6 mg Mn/day (Kondakis, 1993), but data have not been
supplied to substantiate this estimate. Because of the uncertainty in the amount of
manganese in the diet, it is difficult to estimate a total oral intake. The lack of dietary
data is recognized as a source of significant uncertainty in this assessment.
The individuals in this study were submitted to a neurologic examination, the
score of which represents a composite of the presence and severity of 33 symptoms
(e.g., weakness/fatigue, gait disturbances, tremors, dystonia). Whole blood and hair
manganese concentrations were also determined. The mean concentration of
manganese in hair was 3.51. 4.49 and 10.99 u.g/g dry weight for areas A, B and C,
respectively (p<0.001 for area C vs. A). The concentration of manganese in whole blood
did not differ between the three areas, but this is not considered to be a reliable indicator
MANGANES.VI VI-8 08/09/93
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of manganese exposure. The mean (x) and range (r) of neurologic scores were as
follows:
Area A (males: x=2.4, r=0-21; females: x=3.0, r=0-18;
both: x=2.7, r=0-21).
Area B (males: x=1.6, r=0-6; females: x=5.7, r=0-43;
both: x=3.9, r=0-43).
Area C (males: x=4.9, r=0-29; females: x=5.5, r=0-21;
both: x = 5.2, r = 0-29).
A higher neurological score indicates an increased frequency and/or severity of the
33 symptoms that were evaluated. The authors indicate that the difference in mean
scores for area C vs. A was significantly increased (Mann-Whitney z=3.16, p=0.002 for
both sexes combined), indicating possible neurologic impairment in people living in Area
C. In a subsequent analysis, logistic regression indicated that there is a significant
difference between areas A and C even when both age and sex are taken into account
(Kondakis, 1990). Therefore, the LOAEL for this study is defined by Area C
(mean=1950 u,g/L) and the NOAEL by Area B (mean=167 jig/L).
Additional concern for possible health effects resulting from an excessive intake
of manganese has come from studies with infants. Collipp et al. (1983) found that hair
manganese levels in newborn infants was found to increase significantly from birth (0.19
u.g/g) to 6 weeks of age (0.865 ug/g) and 4 months of age (0.685 u.g/g) when the infants
were given formula, but that the increase was not significant in babies who were breast-
fed (0.330 u,g/g at 4 months). While human breast milk is relatively low in manganese
(7-15 u,g/L), levels in infant formulas are 3-100 times higher. It was further reported in
this study that the level of manganese in the hair of learning disabled children (0.434
MANGANES.VI VI-9 08/09/93
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jig/g) was significantly increased in comparison with that of normal children (0.268 (ig/g).
Other investigators have also reported an association between elevated hair levels of
manganese and learning disabilities in children (Barlow and Kapel, 1979; Pihl and
Parkes, 1977). Although no causal relationship has been determined for learning
disabilities and manganese intake, further research in this area is warranted. High levels
of manganese in infant formulas may be of concern because of the increased absorption
and retention of manganese that has been reported in neonatal animals (Lonnerdal et
al., 1987). Also, manganese has been shown to cross the blood-brain barrier, with the
rate of penetration in animal experiments being 4 times higher in neonates than in adults
(Mena, 1974). It was suggested by Dieter et al. (1992) thai "if there were a toxicological
limit to manganese according to the principles of preventive health care, then it would
have to be set at 0.2 mg/L of manganese for infants as a group at risk..."
Although conclusive evidence is lacking, some investigators have also linked
increased intakes of manganese with violent behavior. Gottschalk et al. (1991) found
statistically significantly elevated levels of manganese in the hair of convicted felons
(1.62±0.173 ppm in prisoners compared with 0.35±0.020 ppm in controls). The authors
suggest that "a combination of cofactors, such as the abuse of alcohol or other chemical
substances, as well as psychosocial factors, acting in concert with mild manganese
toxicity may promote violent behavior." Caution should be exercised to prevent reading
too much into these data, but support for this hypothesis is provided by studies of a
population of Aborigines in Groote Eylandt. Several clinical symptoms consistent with
manganese intoxication are present in about 1% of the inhabitants of this Australian
island and it may not be coincidental that the proportion of arrests in this native
MANGANES.VI VI-10 08/09/93
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population is the highest in Australia (Cawte and Florence, 1989; Kilburn. 1987). The
soil in this region is very high in manganese (40,000-50,000 ppm), and the fruits and
vegetables grown in the region are also reported to be high in manganese. Quantitative
data on oral intakes have not been reported, but elevated concentrations of manganese
have been determined in the blood and hair of the Aborigines (Stauber et al., 1987). In
addition to the high levels of environmental manganese, other factors common to this
population may further increase the propensity for manganism: high alcohol intake,
anemia, and a diet deficient in zinc and several vitamins (Florence and Stauber, 1983).
Most of the studies of the health effects of manganese exposure in humans
involve inhalation exposures. They tend to be collections of clinical studies, simply listing
observations rather than analytical epidemiologic studies, which test statistical
associations between exposure and effects. In addition, most of the studies have been
cross-sectiona! in approach rather than the preferred prospective or retrospective design.
Limitations to these studies include the inability to obtain incidence rates or to examine
the effects of exposure duration as well as selection biases and lack of appropriate
controls. The levels of exposure in the following reports are time weighted averages.
Flinn et al. (1941) described neurotoxic effects in 34 workers exposed to
manganese in ore crushing mills. The U.S. EPA (1984) reported that 11/34 workers had
neurologic symptoms indicative of manganese poisoning; those most affected had an
average length of exposure to manganese of 5.3 years and those least affected, 2.4
years. All 11 cases of manganism occurred in workers exposed to 30-180 mg Mn/m3.
Nine workers exposed to <30 mg Mn/m3 had no signs of manganese poisoning. In
MANGANES.VI VI-11 08/09/93
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addition to neurotoxic effects, Flinn et al. (1941) also found evidence of hematologic
effects in humans. Those most affected neurologically also had a low white cell count,
which became more pronounced with the progress of rnanganisrn.
Kesic and Hausler (1954) found hematologic effects in 52 exposed miners without
symptoms of manganism. The miners had higher mean levels of erythrocytes,
hemoglobin, and monocytes compared with levels in 60 sawmill workers of similar age
and social conditions. The level and duration of exposure were not specified.
Ansola et al. (1944a,b) found neuroioxic effects in 12/72 miners exposed to
62.5-250 mg Mn/m3 for 178 days. The classic study by Rodier (1955) described clinical
details of cases of manganese poisoning in miners exposed to 250-450 mg Mn/m3. The
length of exposure varied from 1 month to 10 years. Schuler et al. (1957) studied 83
miners exposed to 1.5-16 mg Mn/m3 for 9 months to 16 years and found neurotoxic
effects among 15 workers.
Sabnis et ai. (1966) found no manganism among workers (number unspecified)
in a ferromanganese alloy factory exposed to <2.3 mg Mn/m3, but did find cases
(number unspecified) of manganism among those who were exposed to 8.4 mg Mn/m3.
The duration of exposure was not specified.
Tanaka and Lieben (1969) studied 117 workers in industrial plants exposed to
5-30 mg Mn/m3, and 38 workers exposed to <5 rng Mn/m3, which is the Threshold Limit
value (TLV) established for occupational exposures by ACGIH (1986). They reported
MANGANES.VI VI-12 08/09/93
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seven cases of manganism among those exposed above the TLV. The length of
exposure was not reported. A subsequent clinical report by Cook et al. (1974) included
workers from these plants.
Emara et al. (1971) found manganism in 8/36 workers exposed to 6.2-42.2 mg
Mn/m3 as manganese dioxide dust in a factory manufacturing dry cell batteries.
Exposure ranged from 1-16 years among the affected cases.
Smyth et al. (1973) reported five cases of manganism among 71 workers in a
ferromanganese production and processing plant. Manganese exposure concentrations
ranged from 0.12-13.3 mg Mn/m3 for fumes and 2.1-12.9 mg Mn/m3 for dust. Length of
exposure ranged from 8-26 years among cases.
Suzuki et al. (1973a) studied workers in a ferromanganese plant who were
exposed to 0.06-4.9 mg Mn/m3 12 hours/day for 12 years. They reported 26 cases
showing signs and symptoms of manganism among 160 workers, which increased with
the number of years of employment. Suzuki et al. (1973b) also found 40/100 workers
affected by exposure to 3.2-8.6 mg Mn/m3 for 1.7-15.3 years.
The biochemical effects of manganese exposure have been studied by Jonderko
et al. (1971, 1973, 1974). In the 1971 study, workers exposed to manganese who did
not exhibit symptoms or signs of manganism were compared with nonexposed controls.
Lower levels of magnesium, hemoglobin, and reduced glutathione in addition to higher
levels of calcium and cholesterol were found among exposed workers. Interpretation is
MANGANES.VI VI-13 08/09/93
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difficult because the duration and level of exposure were not specified. In the 1973
study, 110 workers exposed to manganese in a steel mill at levels 1.3-50 times above
the maximum allowable concentration for an average of 9 years were compared with 90
unexposed controls. Statistically significant (p<0.01) increases in mean cholesterol.
pMipoproteins and total lipoproteins, as well as increased incidences of hypertension and
atherosclerosis were found in the exposed group. The U.S. EPA (1984) noted that
confounding variables such as smoking and obesity were not considered. In the 1974
study, 34 iron-manganese plant workers were examined during employment and 2-4
years after cessation of occupational exposure. Changes in levels of lactate
dehydrogenase, alanine and aspartate aminotransferase, cholesterol, and glutathione
were found to have normalized after exposure ceased when compared with controls.
Hemoglobin levels increased after cessation of exposure as well.
Chandra et al. (1974) studied clinical and biochemical parameters in 12 cases of
suspected manganism and found a statistically significant (p<0.01) increase in serum
calcium and adenosine deaminase levels, which was greatest in the most severe cases.
The author suggested using serum calcium levels to detect early manganism. Also
reported were lower erythrocyte counts and lower hemoglobin concentrations in the
manganism cases as compared with controls. White cell counts were normal and did
not differ between the two groups.
Saric and Hrustic (1975), studying cardiovascular system effects of manganese
exposure, compared the diastolic and systolic blood pressure of 367 workers in a
ferromanganese plant where there were exposures to 0.39-20.44 mg Mn/m3 with that of
MANGANES.VI VI-14 08/09/93
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189 workers in electrode production within the same plant where exposures were
0.002-0.30 mg Mn/m3. The study also included 203 workers unexposed to manganese.
The length of exposure for 75% of the workers was >4 years. The workers wrth the
highest exposures were found to have the lowest mean systolic blood pressure followed
by the lowest exposed and nonexposed workers. This was true regardless of age. The
lowest mean diastolic blood pressure was found in the unexposed workers followed by
the highest and lowest exposed workers. This was also true for all age groups. Saric
(1978) suggests that an action of manganese ions on the myocardium may be
responsible for cardiovascular system effects. The U.S. EPA (1984) notes, however.
that other potentially confounding risk factors were insufficiently controlled in the study.
Saric et al. (1977) published a report that compared 369 workers exposed to
0.3-20.44 mg Mn/m3 at a ferroalloy plant with 190 workers at an electrode plant exposed
to 0.002-0.03 mg Mn/m3 and 204 workers at an aluminum rolling mill exposed to ambient
levels <0.0001 mg Mn/m3. Signs of manganism were found in 17% of workers in the
ferroalloy plant, 6% in the electrode plant, and 0% in the aluminum plant. The ferroalloy
workers were subsequently categorized into three groups by mean manganese
concentrations at working places: <5 mg/m3, 9-11 mg/m3 and 16-20 mg/m3. Table VI-2
presents the findings of effects at different levels of exposures and suggests that slight
neurologic disturbances may occur at exposures <5 mg/m3 and appear to be more
prevalent at higher exposures.
Chandra et al. (1981b) studied neurotoxic effects in welders from a heavy
engineering shop, a railway workshop and a ship repair shop. Welders in the heavy
MANGANES.VI VI-15 08/09/93
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TABLE VI-2
Ferroalloy Workers with Neurologic Signs by Level of Exposure to Manganese*
Mean Manganese Concentrations at Working Places (mg/m3)
Signs
Cogwheel
phenomenon
Difficulty in initiating
voluntary movements
Pathologic reflexes
Tremor at rest
Pathologic reflexes and
tremor at rest
Cogwheel
phenomenon and
tremor at rest
Cogwheel
phenomenon and
pathologic reflexes
Total
-0
(electrode plant)
(n=190)
0
0
1 (0.3%)
10 (5.3%)
0
0
0
11 (5.8%)
-0
(aluminum roling
mill) (n-204)
0
0
0
0
0
0
0
0
<5
(n-369)
1 (0.3%)
2 (0.5%)
6(1.6%)
42(11.4%)
3 (0.8%)
0
0
54 (14.6%)
9-11
(n=17)
0
0
1 (5.7%)
2 (1 1 .8%)
0
0
0
3 (17.6%)
16-20
(n=18)
0
0
1 (5.6%)
2 (11.1%)
0
1 (5.6%)
1 (5.6%)
5 (27.8%)
'Source: Adapted from Sane et al , 1977
MANGANES.VI
VI-16
08/09/93
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engineering shop were exposed to manganese from welding fumes at breathing zone
concentrations of 0.44-0.99 mg/m3 and an airborne mean of 0.31 mg/m3 for 10-31 years.
In the railway workshop, welders' breathing zone concentrations ranged from 0.5-0.8 mg
Mn/m3 with an airborne mean of 0.57 mg Mn/m3 for 2-32 years. Ship repair shop
welders had the highest breathing zone concentration of 0.88-2.6 mg Mn/m3 and
airborne mean of 1.75 mg Mn/m3 for 6-27 years. Neurologic signs in the form of brisk
deep reflexes of limbs and tremors were reported for 5/20 engineering shop welders,
10/20 railway workshop welders, and 9/20 ship repair shop welders. Twenty controls
showed no effects but no statistical analysis nor analysis by person-years was
presented.
A questionnaire was used by Lauwerys et al. (1985) to assess the effect of
manganese dust on male fertility. The manganese-exposed group consisted of 85 male
workers from a factory producing manganese salts. The airborne concentration of
manganese dust ranged from 0.07-8.61 mg/m3 with an average value of -1 mg/m3. The
control group consisted of 81 male factory workers who were never exposed to
manganese. The exposed and control groups were matched for age, age of wife, age
of wife at marriage, duration of employment in the factory, smoking habits, alcohol
consumption, education, professional activity of wife, and desire to have children. While
manganese blood levels were not reported, it was stated that the level was, on average,
2.3 times higher in the exposed group than in the controls. Manganese levels in the
urine were said to fluctuate, but median values of 1.17 and 0.16 tag Mn/g creatinine were
reported for the exposed and control groups, respectively. During their period of
exposure to manganese there was a statistically significant (p<0.05) decrease in the
MANGANES.VI VI-17 08/09/93
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number of children born to exposed workers. There was no indication that any other
factors may have accounted for the difference in fertility between the exposed and
control groups.
Roels et al. (1987a) conducted an epidemiologic study on 141 male workers
exposed to inorganic manganese in a manganese oxide and salt producing plant (mean
age = 34.3 years, mean duration of exposure = 7.1 years, range = 1-19 years). They
were matched with a control group of 104 workers from a nearby chemical plant. The
manganese exposed group was found to have a significantly increased incidence of
several respiratory tract symptoms (coughing, dyspnea during exercise, bronchitis).
Psychomotor tests proved to be the most useful indicator of adverse effects of
manganese on the CMS. The manganese exposed workers exhibited significant adverse
changes in simple reaction time, audioverbal short-term memory capacity, and hand
tremor. Hematologic parameters were all normal except for a significant increase in
neutrophil count. There was also a significant increase in several serum parameters
(ceruloplasmin, copper, ferritin and calcium). There were no monitoring data available,
but during the survey the time-weighted average concentration of total airborne
manganese ranged from 0.07-8.61 mg/m3 with an overall average of -1 mg/m3.
When the above CNS and biologic effects were examined as a function of
blood-manganese and of duration of manganese exposure, no statistically significant
dose-response relationship was found. Blood-manganese levels were related to serum
calcium, hand steadiness and eye-hand coordination. This last parameter was the basis
for the suggestion that the threshold level for blood-manganese is ~1 ^ig/100 ml blood.
MANGANES.VI VI-18 08/09/93
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Levels of manganese in the blood and urine (Mn-B and Mn-U, respectively) of
workers in the above study were reported in a separate publication (Roels et al., 1987b).
Mn-B ranged from 0.1-3.59 u.g/100 mL (arithmetic mean = 1.36) in exposed workers
while levels in the control group ranged from 0.04-1.31 u.g/100 mL (mean = 0.57). Mn-U
levels ranged from 0.06-140.6 u.g/g creatinine (geometric mean = 1.56) in exposed
workers while control levels ranged from 0.01-5.04 (mean = 0.15) |ig/g creatinine. No
relationship was found between Mn-B and Mn-U and neither concentration correlated on
an individual basis with the current level of Mn-air or the duration of manganese
exposure. This is expected as blood and urine levels of manganese are not considered
to be good indicators of manganese exposure.
Carclnoqenicity. There are no epidemiologic studies relating manganese
exposure to cancer occurrence in humans. The available evidence for manganese
carcinogenicity in humans would be rated Group 3 (not classifiable) using the
International Agency for Research on Cancer (IARC) Criteria.
Marjanen (1969) correlated the amount of soluble manganese in cultivated mineral
soil with 5-year cancer incidence rates in Finland and found that cancer incidence rates
decreased with increasing content of manganese. The data were not age-adjusted and
other confounding variables were not considered.
Mutagenicity and Teratogeniclty. No studies were found for humans relating
manganese exposure to mutagenic or teratogenic effects.
MANGANES.VI VI-19 08/09/93
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Summary
Although no clear dose-response relationship is evident, the studies cited in this
report support the association of neurotoxic effects with exposure to manganese in
humans. Other effects, including hematologic, biochemical and cardiovascular have
been reported, but, in most cases, are based on a single study or on studies whose
primary purpose was the investigation of neurotoxic effects. There are no epidemiologic
studies relating manganese exposure to carcinogenic, mutagenic or teratogenic effects
in humans.
The lowest reported exposure levels associated with neurotoxic effects in humans
range from >0.3 mg/m3 for inhaled manganese (Saric et al., 1977; Chandra et al., 1981b;
Roels et al., 1987a). However, the findings reported at 0.3 mg/m3 could not be definitely
attributed to manganese exposure (U.S. EPA, 1984). Levels >5 mg/m3 have been more
consistently associated with neurotoxic effects.
One study of health effects resulting from the ingestion of
manganese-contaminated drinking water found neurotoxic signs and symptoms occurring
at drinking water concentrations >28 mg Mn/L (Kawamura et al., 1941). Another
epidemiologic study suggests increased manganese retention and possible adverse
neurologic effects from chronic ingestion of drinking water containing -2 mg Mn/L
(Kondakiset al., 1989).
MANGANES.VI VI-20 08/09/93
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VII. MECHANISMS OF TOXICITY
Mechanisms of Neurotoxlclty
Manganese is an essential metal in mammals and is required for the activity of
many degradative enzymes such as pyruvate carboxylase, arginase, phosphatases, as
well as the biosynthetic enzymes of lipids and mucopolysaccharides of cartilages
(Venugopal and Lucky, 1978). Exposure to excess amounts of manganese may result
in adverse health effects, primarily of the CNS.
The mechanism by which manganese crosses the blood-brain barrier (BBB) to
gain access to neuronal tissue has not been fully elucidated, but may be a function of
binding to transferrin (Aschner and Aschneri 1990), !n the portal circulation, manganese
binds to a!pha-2-rnacrog!obulin, which is removed by the iiver (Tanaka, 1S82). This
complex, however, cannot cross the BBB. Transferrin, which has a strong affinity for
iron, has also been shown to bind manganese (+3 oxidation state) and may be
responsible for its transport into the brain. This argument is substantiated by the fact
that those regions of the brain that accumulate manganese (e.g., ventral palRdum, gtobus
pallidus and substantia nigra) receive neuronal input from the nucleus accumbens and
the caudate-putamen, both being areas rich in transferrin receptors. More direct
evidence was provided by an experiment in which rats were given a 6-hour intravenous
administration of ferric-hydroxide dexiran complex (Aschner and Aschner, 1990). Tne
uptake of radiolabeled manganese into the brain was significantly (p<0.05) inhibited
following the administration of the iron complex as compared with rats administered iron-
free dextran. It was concluded that iron homeostasis may play an important role in the
MANGANES.VII VII-1 04/13/93
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regulation of manganese transport across the BBB because both metals are transported
by transferrin and may be competing for binding sites.
Several neurotransmitter systems in the brain appear to be affected by
manganese, primarily monoamines such as dopamine, noradrenaline and serotonin (Neff
el ai., 1383; Mustafa and Chandra, 1371), but aiso gamma amino butyric acid (GABA)
(Qianutsos and Murray, 1382). Manganese neurotoxicity is generally associated with a
selective depletion of dopamine in the striatum (Neff et al., 1363; Bemheimer et a!.,
1373). It has been demonstrated that the striatum preferentially accumulates manganese
(Scheuhammer and Cherian, 1381), particularly within the mitochondria (Maynard and
Gotzias, 1355).
Mapping studies have shown that most of the neuronal degeneration attributed
to manganese exposure lies dose to monoamine cell bodies and pathways. However,
histopathology in primates shows rather widespread damage, including the subthalamic
nuclei and the globus pallidus. The globus pallidus was also found to be most severely
affected in an autopsy performed on a worker with manganese poisoning (Yamada et a!.,
1386).
Although there is consensus that the monoaminergic systems, particularly the
dopaminergic system, are affected by excess exposure to manganese, the precise
mechanisms remain obscure. There is a close resemblance between the symptoms of
manganism and Parkinsonian syndrome that has been further substantiated by the
demonstration that several clinical features of manganism respond favorably to therapy
MANGANES.VII VII-2 04/13/33
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with L-dopa in a manner similar to patients with Parkinson's disease (Mena et aJ., 1970).
One theory involves the effect of manganese on brain cytochrome P-450 activity.
LJccione and Maines (1989) demonstrated a high degree of sensitivity of rat striata!
mitochondria to manganese-induced increases in cytochrome P-450 activity. The
authors hypothesized that this increase in mixed function oxidase activity may result in
a concomitant increase in the formation of active oxygen species (e.g., superoxkje
anions) that may result in toxic effects to the dopamine pathways.
Manganese (Mn*3) has also been shown to oxidize dopamine to its cydized
o-quinone (cDAoQ) (Archibald and Tyree, 1987); this is an irreversible process ultimately
resulting in decreased dopamine levels. The formation of cDAoQ may subsequently
initiate the generation of reactive oxygen species that may lead to oxidative stress and
cell death (Segura-Aguilar and Lind, 1989).
It is noteworthy that, while alterations in neurotransmitters have been observed
in rodents administered high levels of manganese, the psychologic disturbances seen
in primates are not observed. Primate brain tissue contains more pigmented areas (e.g.,
the substantia nigra) that are known to sequester manganese. Marsden and Jenner
(1987) hypothesized that the ability of certain drugs to induce parkinsonism in primates
but not in rodents is because of the relative lack of neuromelanin in rodents.
The effects of manganese on the levels of monoamines also appear to be age-
dependent. It has been shown that neonatal rats and mice exposed to manganese from
birth up to 15-30 days of age actually have an increased level of dopamine and
MANGANES.VII VII-3 04/13/93
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norepinephrine in the brain (Chandra et al., 1979; Cotzias et al., 1976; Shukla et al.,
1980).
Parenti et al. (1986) indicated that the alterations of postsynaptic dopaminergic
receptors seen in manganese poisoning may be different from that seen in Parkinson's
disease and that current therapy for Parkinson's disease (administration of L-DOPA) may
be contra-indicated in manganese poisoning. Despite similarities in symptoms, a
comparative study of a worker exposed to manganese in an ore crushing plant and a
52-year-old patient with Parkinson's disease did not reveal any similarity in
neuropathology (Yamada et al., 1986). Since the issue is unresolved, extensive
discussion is beyond the scope of this document and the reader is referred to the cited
literature and to more detailed reviews (Shukla and Singhal, 1984; U.S. EPA, 1984; Seth
and Chandra, 1988).
Studies based on altered neurotransmitter metabolism have examined the
following:
the synthesis of dopamine and the susceptibility of the rate-limiting
synthesizing enzyme, tyrosine hydroxylase (TOH) to manganese;
the changes in TOH activities closely parallel dopamine levels
(Bonilla, 1980; Chandra and Shukla, 1981)
alterations in TOH activity (as well as other monoxygenases) may
also be related to manganese-induced alterations in brain heme
metabolism (Qato and Maines, 1985).
MANGANES.VII VII-4 04/13/93
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VIII. QUANTIFICATION OF TOXICOLOGIC EFFECTS
introduction
The quantification of toxicologic effects of a chemical consists of separate
assessments of noncarcinogenic and carcinogenic health effects. Chemicals that do not
produce carcinogenic effects are believed to have a threshold dose below which no
adverse, noncarcinogenic health effects occur, while carcinogens are assumed to act
without a threshold.
In the quantification of noncarcinogenic effects, a Reference Dose (RfD), [formerly
termed the Acceptable Daily Intake (ADI)] is calculated. The RfD is an estimate (with
uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human
population (including sensitive subgroups) that is likely to be without an appreciable risk
of deleterious health effects during a lifetime. The RfD is derived from a no-observed-
adverse-effect level (NOAEL), or lowest-observed-adverse-effect level (LOAEL), identified
from a subchronic or chronic study, and divided by an uncertainty factor(s) times a
modifying factor. The RfD is calculated as follows:
R,D . (NOAEL or LOAEL) . _
[Uncertainty Facfcr(s) x Modifying Factor]
Selection of the uncertainty factor to be employed in the calculation of the RfD is
based upon professional judgment, while considering the entire data base of toxicologic
effects for the chemical. In order to ensure that uncertainty factors are selected and
MANGANES.VIII VIII-1 01/05/93
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applied in a consistent manner, the U.S. EPA (1993) employs a modification to the
guidelines proposed by the National Academy of Sciences (NAS, 1977,1980) as follows:
Standard Uncertainty Factors (UFs)
• Use a 10-fold factor when extrapolating from valid experimental
results from studies using prolonged exposure to average healthy
humans. This factor is intended to account for the variation in
sensitivity among the members of the human population. [10H]
• Use an additional 10-fold factor when extrapolating from valid results
of long-term studies on experimental animals when results of
studies of human exposure are not available or are inadequate.
This factor is intended to account for the uncertainty in extrapolating
animal data to the case of humans. [10A]
• Use an additional 10-fold factor when extrapolating from less than
chronic results on experimental animals when there is no useful
long-term human data. This factor is intended to account for the
uncertainty in extrapolating from less than chronic NOAELs to
chronic NOAELs. [10S]
• Use an additional 10-fold factor when deriving an RfD from a LOAEL
instead of a NOAEL This factor is intended to account for the
uncertainty in extrapolating from LOAELs to NOAELs. [10L]
Modifying Factor (MF)
• Use professional judgment to determine another uncertainty factor
(MF) that is greater than zero and less than or equal to 10. The
magnitude of the MF depends upon the professional assessment of
scientific uncertainties of the study and data base not explicitly
treated above, e.g., the completeness of the overall data base and
the number of species tested. The default value for the MF is 1.
The uncertainty factor used for a specific risk assessment is based principally
upon scientific judgment rather than scientific fact and accounts for possible intra- and
interspecies differences. Additional considerations not incorporated in the NAS/ODW
guidelines for selection of an uncertainty factor include the use of a less than lifetime
MANGANES.VIII VIII-2 12/18/92
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study for deriving an RfD, the significance of the adverse health effects and the
counterbalancing of beneficial effects.
From the RfD, a Drinking Water Equivalent Level (DWEL) can be calculated. The
DWEL represents a medium specific (i.e., drinking water) lifetime exposure at which
adverse, noncarcinogenic health effects are not anticipated to occur. The DWEL
provides the noncarcinogenic health effects basis for establishing a drinking water
standard. For ingestion data, the DWEL is derived as follows:
DWEL = RfD * (Body weight in k& = mg/L
Drinking Water Volume in L/day
where:
Body weight = assumed to be 70 kg for an adult
Drinking water volume = assumed to be 2 L/day for an adult
The DWEL for manganese, as described in detail later in this chapter, is calculated
from a drinking water-specific RfD (U.S. EPA, 1993). It is assumed that a separate
dietary contribution will be made to the total oral intake.
In addition to the RfD and the DWEL, Health Advisories (HAs) for exposures of
shorter duration (1-day, 10-day and longer-term) are determined. The HA values are
used as informal guidance to municipalities and other organizations when emergency
spills or contamination situations occur. The HAs are calculated using an equation
MANGANES.VIII VIII-3 01/05/93
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similar to the RfD and DWEL; however, the NOAELs or LOAELs are identified from acute
or subchronic studies. The HAs are derived as follows:
NOAEL or LOAEL x (ow) _ _ .
UF x ( L/day)
Using the above equation, the following drinking water HAs are developed for
noncarcinogenic effects:
1. 1-day HA for a 10 kg child ingesting 1 L water per day.
2. 10-day HA for a 10 kg child ingesting 1 L water per day.
3. Longer-term HA for a 10 kg child ingesting 1 L water per day.
4. Longer-term HA for a 70 kg adult ingesting 2 L water per day.
The 1-day HA calculated for a 10 kg child assumes a single acute exposure to the
chemical and is generally derived from a study of <7 days duration. The 10-day HA
assumes a limited exposure period of 1-2 weeks and is generally derived from a study
of <30 days duration. The longer-term HA is derived for both the 10 kg child and a 70
kg adult and assumes an exposure period of -7 years (or 10% of an individual's lifetime).
The longer-term HA is generally derived from a study of subchronic duration (exposure
for 10% of animal's lifetime).
The U.S. EPA categorizes the carcinogenic potential of a chemical, based on the
overall weight-of-evidence, according to the following scheme:
Group A: Human Carcinogen. Sufficient evidence exists from
epidemiology studies to support a causal association between exposure
to the chemical and human cancer.
MANGANES.VIII VIII-4 01/05/93
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Group B: Probable Human Carcinogen. Sufficient evidence of
carcinogenicity in animals with limited (Group B1) or inadequate (Group
B2) evidence in humans.
Group C: Possible Human Carcinogen. Limited evidence of
carcinogenicity in animals in the absence of human data.
Group D: Not Classifiable as to Human Carcinoqenicttv. Inadequate
human and animal evidence of carcinogenicity or for which no data are
available.
Group E: Evidence of Noncarcinogenicitv for Humans. No evidence of
carcinogenicity in at least two adequate animal tests in different species or
in both adequate epidemiologic and animal studies.
If toxicologic evidence leads to the classification of the contaminant as a known,
probable or possible human carcinogen, mathematical models are used to calculate the
estimated excess cancer risk associated with the ingestion of the contaminant in drinking
water. The data used in these estimates usually come from lifetime exposure studies
using animals. In order to predict the risk for humans from animal data, animal doses
must be converted to equivalent human doses. This conversion includes correction for
noncontiguous exposure, less than lifetime studies and for differences in size. The
factor that compensates for the size difference is the cube root of the ratio of the animal
and human body weights. It is assumed that the average adult human body weight is
70 kg and that the average water consumption of an adult human is 2 L of water per
day.
For contaminants with a carcinogenic potential, chemical levels are correlated with
a carcinogenic risk estimate by employing a cancer potency (unit risk) value together
with the assumption for lifetime exposure from ingestion of water. The cancer unit risk
is usually derived from a linearized multistage model with a 95% upper confidence limit
MANGANES.VIII VIII-5 12/31/92
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providing a low dose estimate; that is, the true risk to humans, while not identifiable, is
not likely to exceed the upper limit estimate and, in fact, may be lower. Excess cancer
risk estimates may also be calculated using other models such as the one-hit, Weibull,
log'rt and probrt. There is little basis in the current understanding of the biologic
mechanisms involved in cancer to suggest that any one of these models is able to
predict risk more accurately than any other. Because each model is based upon
differing assumptions, the estimates derived for each model can differ by several orders
of magnitude.
The scientific data base used to calculate and support the setting of cancer risk
rate levels has an inherent uncertainty that is due to the systematic and random errors
in scientific measurement. In most cases, only studies using experimental animals have
been performed. Thus, there is uncertainty when the data are extrapolated to humans.
When developing cancer risk rate levels, several other areas of uncertainty exist, such
as the incomplete knowledge concerning the health effects of contaminants in drinking
water, the impact of the experimental animal's age, sex and species, the nature of the
target organ system(s) examined and (he actual rate of exposure of the internal targets
in experimental animals or humans. Dose-response data usually are available only for
high levels of exposure and not for the lower levels of exposure closer to where a
standard may be set. When there is exposure to more than one contaminant, additional
uncertainty results from a lack of information about possible synergistic or antagonistic
effects.
MANGANES.VIII VIII-6 12/31/92
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Noncarcinogenic Effects of Manganese In the Diet
The health effects associated wfth the ingestion of manganese are highly
dependent on its bioavailability. This may be affected by several factors including
species, age, form of manganese, medium (e.g., drinking water vs. food), nutritional
status and other dietary constituents. These factors, addressed in Chapters HI, V and
VI, will also be discussed below, particularly as they impact the quantitative risk
assessment of manganese.
It is well recognized that there are significant differences in species' requirements
for manganese intakes and in the health effects observed in different species resulting
from excessive manganese exposure. Primates are acknowledged to be a better
experimental animal than rodents for studying the neurobehavioral manifestations of
manganese intoxication (U.S. EPA, 1984). In the brain, several neurotransmrtter
systems appear to be affected by excess manganese exposure such as dopamine,
noradrenaline and serotonin (Neff et al., 1969). Mapping studies have shown that most
of the neuronal degenerative alterations in the CNS syndrome of toxicity (manganism)
occur where pathways of the monoamines are anatomically located (Pentschew et al.,
1963). It has been proposed that the accumulation of manganese in the brain occurs
more readily in pigmented tissue, which is distributed differently in primates than in
rodents. Also, the human neurobehavioral deficits (e.g., tremor, gait disorders)
stemming from manganese toxicity can be reproduced in primates, but not in rodents.
For these reasons, rodent species may be less appropriate for studying manganese
neurotoxicity.
MANGANES.VIII VIII-7 08/09/93
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Although no recommended dietary allowance (RDA) has been established for
manganese, it is recognized as an essential element for the activity of many enzymes
in humans. Several studies have been performed to determine the average daily intake
of manganese from a "typical" American diet. The Total Diet Study conducted in the
United States between 1982 and 1986 reported the mean dietary intake to be 2.2 mg
Mn/day for women and 2.7 mg Mn/day for men (Pennington et al., 1989). The NAS
Food and Nutrition Board has estimated that, based upon manganese intake and
balance studies, a 2-5 mg daily intake of manganese (for food and beverages, which
includes drinking water) is adequate and safe for adults (NRC, 1989). A World Health
Organization report (WHO, 1973) on trace elements in human nutrition suggests that
dietary manganese intakes of 8-9 mg/day are safe, since balance studies on normal
men and women consuming these levels revealed no evidence of manganese toxicity.
The criteria for determining safety were not presented, but it may be assumed that no
toxic effects were observed at these levels. Schroeder et al. (1966) reported that
patients (number not specified) given 30 mg manganese citrate (equivalent to 9 mg
manganese) daily for many months did not show any signs of toxicity. Assuming the
patients consumed another 2.5 mg manganese in their diet, the total intake would be
-11.5 Mn/day. Schroeder et al. (1966) has estimated that a 2300 calorie vegetarian diet
of whole grains, fresh vegetables, fruits, nuts and tea (all rich sources of manganese)
would provide an intake as high as 13-20 mg Mn/day. These levels are also considered
to be safe. However, the bioavailability of manganese from various food sources may
vary substantially. For example, several constituents of vegetarian diets (e.g., fiber,
lectins, phytates) may result in decreased bioavailability of manganese. High or low
MANGANES.VIII VIII-8 02/25/93
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levels of other dietary minerals such as iron, calcium and phosphorus may also affect
manganese uptake.
Kawamura et al. (1941) reported on health effects resulting from the ingestion of
manganese-contaminated well water by 25 individuals. The well water had been
contaminated with manganese dissolved from dry cells batteries buried near the well.
The length of exposure to manganese was estimated to be 2-3 months. The
concentration of manganese in the well water was analyzed 7 weeks after the first case
appeared and was determined at that time to be -14 mg Mn/L (as Mn3OJ. However,
when reanalyzed 1 month later, the levels were decreased by about half. Therefore, the
actual exposure was probably to drinking water containing 28 mg Mn/L or higher.
Assuming a daily water intake of 2 L, this represents a dose of at least 56 mg Mn/day,
plus that which was in the diet. This represents a dose about 10-20 times the dietary
intake considered to be safe and adequate by the Food and Nutrition Board of the
National Research Council (NRC, 1989). Health effects included lethargy, increased
muscle tonus, termor and mental disturbances. The elderly were more frequently and
more severely affected; children were affected less. Three deaths occurred, one from
suicide. Upon autopsy, the concentration of manganese in the brain of one case was
found to be 2-3 times higher than in two controls. In the brain, extreme macroscopic
and microscopic changes were seen, especially in the globus pallidus.
Kawamura et al. (1941) also reported excess zinc in the well water, but concluded
that the zinc appeared to have no relation to the reported symptoms and pathologic
changes found in the tissues. This conclusion was based upon the fact that, upon
MANGANES.VIII VIII-9 02/25/93
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autopsy, morphologic changes were observed in the corpus striatum, which is
characteristic of manganese poisoning, but not of zinc poisoning. While manganese
appears to be the cause of toxicity in these individuals, several aspects of this outbreak
are inconsistent with traits of manganism in humans resulting from inhalation exposure.
First, the symptoms appeared to come on very quickly; for example, two adults who
came to tend the members of one family developed symptoms within 2-3 weeks. Also,
the course of the disease was very rapid, progressing in one case from initial symptoms
to death in 3 days. Those who did survive recovered from the symptoms, even before
the manganese content of the well had decreased significantly after removal of the
batteries. This is in contrast to the longer latency period and irreversible damage caused
by inhalation exposure to manganese. These differences may represent differences in
the pharmacokinetics of ingested vs. inhaled manganese, but there is little information
to support this. Therefore, while there is no question that these individuals were
exposed to high levels of manganese, it is not dear that the observed effects were due
to manganese alone.
There was one epidemiologic study of manganese in drinking water performed
by Kondakis et al. (1989). Three areas in northwest Greece were chosen for this study,
with manganese concentrations of 3.6-14.6 vg/L in area A, 81.6-252.6 ^g/L in area B,
and 1800-2300 MQ/L in area C. The total population in the three areas being studied
ranged from 3200 to 4350 people. The study included only individuals over the age of
50 drawn from a random sample of 10% of all households (n = 62, 49 and 77 for areas
A, B and C). The authors reported that "all areas were similar with respect to social and
dietary characteristics," but few details were reported. The individuals chosen were
MANGANES.VIII VIII-10 02/25/93
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submitted to a neurologic examination, the score of which represents a composite of the
presence and severity of 33 symptoms (e.g., weakness/fatigue, gait, disturbances,
tremors, dystonia). Whole blood and hair manganese concentrations were also
determined. The mean concentration of manganese in hair was 3.51, 4.49 and 10.99
nQ/Q dry weight for areas A, B and C, respectively (p< 0.001 for area C vs. A). The
concentration of manganese in whole blood did not differ between the three areas, but
this is not considered to be a reliable indicator of manganese exposure. The mean (x)
and range (r) of neurologic scores were as follows:
Area A (males: x=2.4, r=0-21; females: x=3.0, r=0-18;
both: x = 2.7, r=0-21).
Area B (males: x=1.6, r=0-6; females: x=5.7, r=0-43;
both: x=3.9, r=0-43).
Area C (males: x=4.9, r=0-29; females: x=5.5, r=0-21;
both: x=5.2, r=0-29).
The authors indicate that the difference in mean scores for area C vs. A was
significantly increased (Mann-Whitney z=3.16, p= 0.002 for both sexes combined). In
a subsequent analysis, logistic regression indicated that there is a significant difference
between areas A and C even when both age and sex are taken into account (Kondakis,
1990). Therefore, the LOAEL for this study is defined by Area C (mean = 1950 Mg/L) and
the NOAEL by Area B (mean = 167
The report by Kondakis et al. (1989) is the only epidemiologic study of the effects
associated with low-level ingestion of manganese in drinking water. Most of the studies
of the health effects of manganese exposure in humans involve inhalation exposures.
MANGANES.VIII VIII-11 02/25/93
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Animal studies of manganese toxic'rty arising from oral exposure generally do not
provide evidence of a dose-response relationship for neurologic effects similar to those
observed in humans. Reported effects in rodents exposed to manganese in drinking
water include alterations in neurotransmitter systems but not neurobehavioral effects.
It is uncertain whether the effects on neurotransm'rtters should be defined as adverse,
since they could represent compensatory responses. Also, these effects are highly
dependent on many variables, such as the exposure regimen and the age of the animal.
Several studies with monkeys exposed to large doses of manganese by
parenteral routes have consistently reported extrapyramidal symptoms and histologic
lesions that resemble those described in advanced human manganism (U.S. EPA, 1984).
However, only one limited study of oral administration has been published (Gupta et al.,
1980). Four rhesus monkeys (M. mulatta) administered an oral dose of 6.9 mg
Mn/kg/day (25 mgTkg MnClj«4H2O) for 18 months developed neurologic signs and
showed histologic evidence of damage to the substantia nigra. No biochemical data
were reported.
Chandra et al. (1979a) reported CNS effects in growing male mice exposed to 1
mg Mn/kg bw/day (3 |ig Mn/mL drinking water x 10 ml_ water/day + 0.03 kg bw) for the
first 6 months of life. These effects included a significant increase in motor activity at
60 and 90 days associated with a significant elevation in levels of dopamine and
norepinephrine. However, the reported exposure levels are below the NAS
recommendation for rodents for the average daily intake of 3-6 mg/kg/day deemed
necessary for development (MAS, 1980) making their validity questionable, particularly
MANGANES.VIII VIII-12 02/25/93
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given the recent studies by Lown et al. (1984) and Gianutsos and Murray (1982). The
studies by Chandra and coworkers have also been questioned because of the strain of
animals used (I.T.R.C. rats and mice). There are no historic data on this strain and it
is possible that metabolic or other differences between strains account for discrepancies
between these and other studies.
Singh et a!. (1979) reported significant alterations of brain enryTTiSS in mature rats
exposed to 4.4 mg Mn/kg in drinking water for 30 days. The study found no brain
morphologic changes but noted that biochemical changes occur before morphologic
damage is visible under light microscope.
The next lowest reported dose producing CNS effects has been reported by Lai,
Leung and colleagues (Lai et a!., 138 la, 19S2a, 1984; Leung et a!., 1981, 1932;
Nachtman et al., 1986). In developing and aging rats orally exposed to 38.9 mg
Mn/kg/day (1 mg MnC12»4H2O/mL drinking water = 0.278 mg Mn/mL x 0.49 mL/day +
0.35 kg = 38.9 mg Mn/kg) different neurotoxic effects were reported depending on the
age of the rat and the duration of exposure. Lai et al. (I982a) concluded that although
the rat may not appear to serve as an idea! mode! for studying the neurotoxic effects of
manganese, some neurochemical effects may be discernible when selected analyses are
made at the appropriate period.
Chandra and Shukla (1981) exposed young male rats to 38.9 mg Mn/kg/day
(0.278 mg Mn/mL x 0.49 mL/day + 0.350 kg = 38.9 mg Mn/kg) as 1 mg MnCI3«4H,O/mL
drinking water for as long as 360 days. Doparnine, norepinephrine and homovanillic acid
MANGANES.VIII VIII- 13 02/25/93
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levels were found to increase initially, then to return to normal and finally to decrease
significantly after 300 days of exposure. The authors suggested that the early biochemi-
cal elevations might explain the psychiatric signs often associated with the early phases
of manganese toxicrty, while later biochemical declines may produce the neurologic
manifestations.
Newborn rats exposed to 150 mg Mn/kg/day by gavage for 41 days displayed a
rigid and unsteady gait from 15-22 days of age (Kristensson et al., 1986). The gait was
normal by 44 days of age. Transient effects were also observed in some
neuretransmitter levels.
Bonilla and Diez-Ewald (1974) found decreased dopamine levels in female adult
rats exposed in drinking water for 7 months to 255 mg Mn/kg/day (2.18 mg Mn/mL x 35
ml_ + 0.300 kg = 255 mg Mn/kg). Behavioral and histologic parameters were not
examined.
The studies reviewed above show marked inconsistencies, even conflicts in the
dose-effect function for neurologic effects. Liver effects have also been reported after
oral manganese exposure, but these data are also not consistent. Wasserman and
Wasserman (1977) reported ultrastructural changes of the liver cell in young male rats
exposed to 12.2 mg Mn/kg/day in drinking water for 10 weeks. Shukla et al. (1978)
found biochemical changes in the livers of adult male rats exposed to 4.4 mg Mn/kg/day
for 30 days. Kimura et al. (1978), however, reported no liver effects in male rats
exposed to 56.4 mg Mn/kg/day for 3 weeks. Leung et al. (1982) found higher liver MAO
MANGANES.VMI VIII-14 02/25/93
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plateau values in female rats exposed to 38.9, 389 or 778 mg Mn/kg/day for 80 days;
however, the effects were not dose related. Hietanen et al. (1981) administered 700 mg
Mn/kg/day in drinking water to rats and found changes in several hepatic enzyme
activities at 1 week but not at 6 weeks.
Oral administration of manganese to experimental animals has also produced
some reproductive effects. Laskey et al. (1982) reported a dose-related decrease in
serum testosterone concentrations in young male rats exposed for 100 days to 20, 55
or 177.5 mg Mn/kg/day in the diet. In addition, reduced fertility was found after 224 days
in female mice exposed to 177.5 mg Mn/kg/day. Gray and Laskey (1980) reported
decreased weight of testes, seminal vesicles and preputial glands in male mice exposed
in the diet to 143 mg Mn/kg/day for 90 days.
There are several issues to be considered in performing a risk assessment for
ingested manganese. One factor is that of selecting the most appropriate species. The
most sensitive and subtle expressions of manganese toxicity reflect action upon the
CNS. The neurobehavioral effects observed in humans, however, have not been
reproduced in rodents by oral, inhalation or parenteral routes. These exposure routes
have produced the characteristic neurobehavioral effects in monkeys. Thus, from the
standpoint of modeling the neurotoxic effects observed in humans, studies involving
rodents are of limited use.
Another issue to be considered is that of the route of administration of
manganese. While the toxicity of ingested manganese is low in laboratory animals,
MANGANES.VIII VIII-15 02/25/93
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adverse effects on the central nervous system are apparent at much lower doses
following exposure by inhalation. Therefore, in deriving an RfD, an oral study is required
because of the large amount of uncertainty involved in route-to-route extrapolation.
Unfortunately, only one primate study involving oral administration of manganese is
available (Gupta et al., 1980), and it is confined to a single dose level, 6.9 mg/kg/day,
that is associated with significant toxicity.
Finally one of the more significant factors that appears to impact the toxicity of
manganese is the medium in which it is ingested, particularly food vs. drinking water.
Accordingly, the following discussion is divided into two sections, the first describing the
development of a dietary RfD for manganese and the second describing the
development of a drinking water RfD.
Development of the Dietary RfD for Manganese
Schroeder et al. (1966) reported that patients (number not specified) given 9 mg
Mn/day (as manganese citrate) for many months did not show any signs of toxicity.
Assuming the patients consumed another 2.5 mg manganese in their normal diet, the
total intake would be -11.5 mg Mn/day. Schroeder et al. (1966) has estimated that a
vegetarian diet may provide a manganese intake as high as 13-20 mg/day. These levels
are also considered to be safe, but it should be kept in mind that the manganese present
in a vegetarian diet may be less bioavailable.
The NAS Food and Nutrition Board has estimated a daily intake of 2-5 mg Mn for
adults as being "safe and adequate' (NRC, 1989) and the WHO (1973) concluded that
MANGANES.VIII VIII-16 02/25/93
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there was no evidence of manganese toxicity in individuals consuming 8-9 mg Mn/day
in food. Little information is available to indicate at what levels manganese In the diet
presents a health threat. It is clear however, that the dietary RfD should be establishied
above the "safe and adequate levels" of 2-5 mg/day established by NRC.
Based on information from the NAS Food and Nutrition Board (NRC. 1983).
Schroeder et al. (1966), and WHO (1973), a dietary manganese intake of 10 mg/day has
been chosen to represent a chronic oral human NOAEL Furthermore, because of the
efficient homeostatic control of manganese and its essentiality, this level is thought to
be safe for all humans. For a 70 kg adult, this dose converts to 0.14 mg Mn/kg bw/day.
RfD (food) - °'14 m9 Mn/kg/day __ Q 14 mg Mn/kgfday
where:
0.14 mg Mn/kg/day
1
a chronic human NOAEL
uncertainty factor to be used in
conjunction with chronic human data
identifying a NOAEL that is safe for ail
subpopulations.
The oral RfD of 0.14 mg Mn/kg/day for a dietary intake was verified by the RfD
Work Group in September 1992 (U.S. EPA, 1993). It is emphasized that this oral RfD
is based on total dietary intakes; a separate RfD was derived for manganese in drinking
water.
MANGANES.VIII
VIII-17
08/09/93
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It is important to recognize, however, that while the RfD process involves the
determination of a single point estimate of an oral intake, a range of intakes more
appropriately fits the science. This is consistent with the definition of the RfD, which is
associated "with uncertainty spanning perhaps an order of magnitude." Numerous
factors, both environmental (e.g., the presence or absence of many dietary constituents)
and biological or host-related (e.g., age, nutritional status, alcohol consumption), can
significantly influence an individual's uptake of manganese from the diet. As discussed
in Chapter III, there is significant variability in the absorption of manganese by humans.
The determination of a single intake of manganese in the diet must be recognized as a
process that is limited in its ability to reflect the variable nature of manganese toxicity.
It may both over- and underestimate the risk depending on the specific combination of
environmental and individual circumstances.
Development of the Drinking Water RfD for Manganese
In contrast to manganese in the diet, two studies using humans have associated
high levels of manganese in drinking water with neurologic effects. The first, a case
study by Kawamura et al. (1941) reported frank effects in humans who drank well water
contaminated with manganese at levels of about 28 mg/L for a few months (see Chapter
VI for full discussion). A Greek epidemiologic study by Kondakis et al. (1989; also
described in Chapter VI) examined individuals over 50 years of age who consumed
water containing manganese at concentrations of 3.6-14.6 ug/L (Area A, mean = 9.1
ug/L); 81.6-252.6 ug/L (Area B, mean = 167 ug/L); or 1600-2300 ug/L (Area C, mean =
1950 ug/L). No effects were observed in individuals from Area B, but some degree of
MANGANES.VIII VIII-18 08/19/93
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neurologic impairment was reported in residents of Area C. This study is used to
support the calculation of a drinking water RfD for manganese.
RfD (wate* = °'167 mg Mn/L x 2 Uday - 0.0048 mjkg/day
1 70 kg (rounded to 0.005 mg/kg/day)
where:
0.167mgMn/L = drinking water concentration of manganese
consumed for a lifetime without adverse health
effects (Kondakis et al.. 1989)
2 Uday = assumed water consumption by an adult
70 kg = assumed body weight of an adult
1 = uncertainty factor to be used in conjunction
with chronic human data identifying a NOAEL
that is safe for all subpopulations
Quantification of Noncarcinoqenic Effects for Manganese in Drlnklnq Water
Derivation of 1-Day and 10-Day HAs. There are two human studies involving
exposure through drinking water. Kondakis et al. (1989) reported increased manganese
content in the hair and possible neurologic impairment of individuals drinking water
containing -2 mg Mn/L. Kawamura et al. (1941) reported that 3 of 25 individuals died
following a few months of exposure to at least 28 mg Mn/L of contaminated well water.
Several others exhibited neurologic impairment, but children were not affected to the
degree that adults were. The study by Kondakis et al. (1989) was used to establish a
water-specific RfD of 0.005 mg/kg/day for manganese. Assuming a body weight of 70
MANGANES.VIII VIII-19 10/08/93
-------
kg and a drinking water consumption of 2 L/day, this RfD is equivalent to about 0.2 mg
Mn/L drinking water. However, this RfD is for chronic exposure to manganese. Acute
exposures do not warrant the same concern. Also, children appear to be less sensitive
to the effects of ingested manganese than are adults, particularly the elderly. This is
substantiated by the greater requirement of manganese for growth and health
maintenance in children (NRC, 1989) and also by the Japanese poisoning (Kawamura
et a!., 1941) that reported frank effects (including neurologic impairment and deaths) in
elderly humans but no effects in children up to 10 years of age.
Unfortunately, there are relajively few data that are appropriate to use in setting
short-term health advisories. The NRC has estimated that for infants 6 months to 1 year
of age, an intake of 0.6-1 mg Mn/day is safe and adequate. Taking the upper end of
this range (1 mg Mn/day) and assuming that the infant's nutrition comes from a
maximum of about 1 L of formula per day, this would correspond to a manganese
concentration of 1 mg/L. This concentration is higher than the NOAEL of 0.2 mg/L but
lower than the LOAEL of 2 mg/L, identified by Kondakis et al. (1989).
1- and 10-day HA =
1 Uday
- 1 mgIL
where:
1 mg/day
1 L/day
MANGANES.VIII
intake of manganese considered to be "safe
and adequate" for infants (NRC, 1989)
assumed water consumption by a child
VIII-20
08/19/93
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uncertainty factor to be used with intake known
to be safe for short-term ingestion by humans
Derivation of Lonqer-term HA. As with the 1- and 10-day HAs, there are no
studies appropriate for the derivation specifically of a longer-term hearth advisory. The
basis for the water-specific RfD is considered to provide the best basis upon which to
base a longer-term HA.
It is recommended that this level, 0.2 mg Mn/L, be adopted for the longer-term
health advisory for manganese. Calculation of separate concentrations for children and
adults is not warranted.
Assessment of Lifetime Exposure and Derivation of a DWEL In the study
by Kawamura et a). (1941), three people died and several others were neurologically
impaired following exposure for several months ID drinking water containing at least 28
mg Mn/L. The study by Kondakis et al. (1989) suggests that a lifetime exposure to
drinking water containing -2 mg Mn/L results in an increased retention of manganese
(as demonstrated by an increased concentration of manganese in hair) and possible
neurologic impairment. It is noted, however, that the confidence in this assessment is
compromised by the lack of data on dietary manganese in the three populations under
study. Also, many of the endpoints scored in the neurological examination are not
specific for manganese poisoning, and are, in fact, associated with the normal process
of aging.
MANGANES.VIII VIII-21 08/19/93
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Based on the study by Kondakis et al. (1989), the RfD/RfC Work Group verified
a water-specific RfD for manganese of 0.005 mg/kg/day (U.S. EPA, 1993). This is used
as the basis for the DWEL:
DWEL = a005 ^kgfday x 70 kg __ Q 1?5 L (rQun(Je(j tQ Q2 mgfL)
2 Uday
where:
0.005 mg/kg/day = RfD (drinking water-specific)
70 kg = assumed body weight of an adult
2 L/day = assumed water consumption of an adult
Because the DWEL is based on a water-specific RfD that assumes a normal
dietary intake of manganese, it is not necessary to factor in a relative source contribution
when establishing drinking water standards. This assumption is made primarily because
the differences in the bioavailability of manganese in food as compared with that of
manganese in water may be such that it is inappropriate to add these intakes together.
Unfortunately, while it is agreed that the bioavailability of manganese may vary
substantially, relatively few data are available to quantitate these differences, and the
number of variables that may affect the uptake of manganese are such that to determine
a single value for the absorption of manganese from any medium is not appropriate.
These issues have been discussed in Chapter III of this document.
While the RfD process involves the determination of a single point estimate of an
oral intake, it must be recognized that a range of intakes more appropriately fits the
science. This is consistent with the definition of the RfD, which is associated "with
MANGANES.VIII VIII-22 08/19/93
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uncertainty spanning perhaps an order of magnitude." Numerous factors, both
environmental (e.g., the presence of high or low levels of other inorganics in drinking
water) and biological or host-related (e.g., age, nutritional status, alcohol consumption).
can significantly influence the uptake of manganese by an individual. The determination
of a single concentration of manganese in drinking water, then, must be recognized as
a process that is limited in its anility to reflect the variable nature of manganese toxicity.
Finally, while a concentration of 0.2 mg Mn/L is recommended for health baseJ
reasons, it is noted that a concentration of <0.05 mg Mn/L should be maintained to
prevent undesirable taste and discoloration (U.S. EPA, 1984).
VVeiqht-of-Evidence for Carcinogenic Effects
No epidemiologic information relating manganese exposure to cancer occurrence
in humans is available. Although there is some evidence of carcinogenic activity in
laboratory animals exposed to manganese, problems exist with regard to the relevance
of these studies to human carcinogenesis.
In a 2-year bioassay, groups of F344 rats (70/sex) were administered 0, 1500,
5000 or 15,000 ppm manganese sulfate monohydrate (NTP, 1992). These dietary
concentrations were reported to be equivalent to an intake ranging from 91 mg/kg/day
(30 mg Mn/kg/day) for low-dose males to 1019 mg/kg/day (331 mg Mn/kg/day) for high-
dose males. For females, the range of intakes was from 81 mg/kg/day (26 mg
Mn/kg/day) for the low-dose group to 833 rng/kg/day (270 rng Mn/kg/day) for the high-
MANGANES.VIII VIII-23 08/19/93
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dose males. For females, the range of intakes was from 81 mg/kg/day (26 mg
Mn/kg/day) for the low-dose group to 833 mg/kg/day (270 rng Mn/kg/day) for the high-
dose group. No increases in any tumor type reported were attributed to manganese
exposure in rats.
In the same study, groups of B6C3F1 mice (70/sex) were administered 0, 1500,
5000 or 15,000 ppm manganese sulfate monohydrate (NTP, 1992). These dietary
concentrations were reported to be equivalent to an intake ranging from 194 mg/kg/day
(63 mg Mn/kg/day) for low-dose males to 2222 mg/kg/day (722 mg Mn/kg/day) for high-
dose males. For females, the range of intakes was from 238 mg/kg/day (77 mg
Mn/kg/day) for the low-dose group to 2785 mg/kg/day (905 mg Mn/kg/day) for the high-
dose group. Incidences of thyroid follicular cell hyperplasia were significantly greater in
high-dose males and females than in controls. The incidence of follicular cell adenomas
was 0/50, 0/43, 0/51 and 3/50 (6%) for control, low-, mid- and high-dose maies,
respectively. The historical control range for males was reported to be 0-4%. For
females, the incidence of follicular cell adenomas was 2/50, 1/50, 0/49 and 5/51 (10%)
for control, low-, mid- and high-dose groups, respectively. The historical control range
for females was reported to be 0-9%. None of the reported incidences were statistically
significantly increased over historical controls, nor were they clearly dose-related. Also,
the foiiicuiar ceil tumors were seen only at the termination of the study (729 days) and
only slightly increased relative to the historical control range in the highest dose groups.
NTP (1992) reported that the manganese intakes in the high-dose mice was 107 times
higher than the recommended dietary allowance. While NTP concluded that the data
provide "equivocal evidence" of carcinogenic activity of manganese in mice, the
MANGANES.VIII VIII-24 08/19/93
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relevance of these findings to human carcinogenesis is questionable, particularly
because of the very large intakes of manganese required to elicit a response seen only
at the end of the study, and at frequencies not statistically significantly different from
historical controls.
In a study by DiPaolo (1964), a larger percentage of DBA/1 mice exposed
subcutaneously and intraperitoneally to manganese chloride developed lymphosarcomas
compared with controls. A thorough evaluation of these results was not possible
because they were published in abstract form and lacked sufficient detail (U.S. EPA,
1984). Stoner et al. (1976) found a higher frequency of lung tumors in strain A/Strong
mice exposed intraperitoneally to manganese sulfate compared with controls. The study
results, although suggestive of carcinogenic activity, do not conclusively meet the criteria
for establishment of a positive response, namely, an increase in the mean number of
tumors per mouse and an evident dose-response relationship (Shimkin and Stoner,
1975). Furst (1978) found an increased incidence of fibrosarcomas at the injection site
in F344 rats exposed intramuscularly to manganese acetylacetonate, but not other
tumors.
In a series of genetic toxicology assays performed by NTP (1992), manganese
sulfate monohydrate was not found to be mutagenic in Salmonella typhimurium strains
TA97, TA98, TA100, TA1535 or TA1537, either with or without metabolic (S9) activation.
Likewise, mutations were not induced in the sex-linked recessive lethal assay in
Drosophila melanogaster. However, sister chromatid exchanges and chromosomal
MANGANES.VIII VIII-25 08/19/93
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aberrations were induced in Chinese hamster ovary cells in the absence of S9; only the
sister chromatid exchange test was positive with S9 (NTP, 1992).
The weight-of-evidence for manganese carcinogenicity is currently rated as Group
D (not classifiable) using the criteria of the U.S. EPA Guidelines for Carcinogen Risk
Assessment (U.S. EPA, 1986a). The classification of Group D was verified (05/25/88)
by the CRAVE Work Group of the U.S. EPA. This classification will be re-evaluated
when the NTP bioassay (NTP, 1992) is available in final form.
Existing Guidelines. Recommendations and Standards
A maximum concentration of 0.05 mg/L has been recommended for manganese
in freshwater to prevent undesirable taste and discoloration (WHO, 1970; U.S. PHS,
1962; U.S. EPA, 1976). No criteria or standards based upon toxicrty have been
proposed. For the protection of consumers of marine mollusks, a criterion for
manganese of 0.1 mg/L for marine waters has been recommended (U.S. EPA, 1976).
The rationale for this criterion has not been specified, but is partially based on the
observation that manganese can bioaccumulate in marine mollusks (U.S. EPA, 1984).
In quantifying acceptable intakes for manganese, it is important to consider the
essentiality of this metal. The Food and Nutrition Board of the National Research
Council (NRC, 1989) has determined the Estimated Safe and Adequate Daily Dietary
Intake (ESADDI) range for manganese to be 0.7-1.5 mg/day for infants and children and
2-5 mg/day for teenagers and adults.
MANGANES.VIII VIII-26 08/19/93
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exposure (Mena et al., 1969, 1974). Mena et al. (1974) reported that the early neonatal
period may be critical for manganese accumulation because very young rats have
increased intestinal absorption and retention of manganese. Other heavy metals show
similarly increased absorption in the young; this does not necessarily mean increased
potential for toxicity because it may reflect a higher nutritional requirement.
The developing fetus may also be at risk. Manganese penetrates the placenta!
barrier (Schroeder et al., 1966) and accumulates in the fetus such that its concentration
is 7-9% higher than in adult tissues (Widdowson et al., 1972). Manganese also
penetrates the blood brain barrier with the rate being 4 times higher in the newborn rat
compared with adults (Mena, 1974). Again, the increased uptake of manganese by the
fetus and neonate may reflect a higher nutritional need and may not necessarily indicate
an increased risk of toxicity.
The aged may be at increased risk for manganese toxicity because of a decrease
in adaptive responsiveness (Rothand and Adleman, 1975). Silbergeld (1982) also points
out that in manganese toxicity, neurotoxicity involves the basal ganglia and
monoaminergic pathways that are themselves commonly affected by aging.
MANGANES.VIII VIII-28 08/19/93
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In a study sponsored by the Food and Drug Administration (Pennington et al.,
1986), the daily intake of 11 essential minerals was estimated based on the consumption
of 234 foods by eight different age-sex groups. The daily intake of manganese was
1.1-1.5 mg/day for infants and children and 1.8-2.7 mg/day for teenagers and adults.
The forementioned studies are all based on a total dietary intake of manganese.
This information was used by the RfD Work Group as the basis for the oral RfD (food),
which was calculated to be 0.14 mg/kg/day (verified in September, 1992). A separate
water RfD of 0.005 mg/kg/day was also verified based on the Greek epidemiologic study
by Kond?kis ot al. (1989). Additional data on the bioavailability of manganese from
water and various foods are needed to increase the level of confidence that can be
placed on these estimates.
Special Groups at Risk
Although several researchers have noted marked differences in individual
susceptibility to inhaled manganese (Rodier. 1955; Penalver, 1955; Cotzias. 1958).
suggesting that an impaired ability to clear inhaled manganese or to excrete absorbed
manganese results in an increased risk of adverse effects, no studies exist to confirm
these hypotheses. Individuals suffering from alcoholism, syphilis and lesions of the
excretory system have been inferred to be at greater risk (U.S. EPA, 1984), but there
is no supporting epidemiologic evidence.
Individuals with iron deficiency show increased rates of manganese absorption.
They are, therefore, assumed to be at greatest risk of adverse effects from manganese
MANGANES.VIII VIII-27 08/19/93
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