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aw $2.0
January 1992
FINAL
DRINKING WATER CRITERIA DOCUMENT
FOR
DALAPON
Health and Ecological Criteria Division
Office of Science and Technology
Office of Water
U.S. Environmental Protection Agency
Washington, DC 20460
en
cvi
HEADQUA:
ENVIRON'-
WASHINi ..
"**\ AGENCY
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January 1992 [j
FINAL
DRINKING WATER CRITERIA DOCUMENT
FOR
DALAPON
Health and Ecological Criteria Division
Office of Science and Technology
Office of Water
U.S. Environmental Protection Agency
Washington, DC 20460
_- -
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TABLE OF CONTENTS
Page
LIST OF FIGURES
LIST OF TABLES viii
FORWORD ix
I. SUMMARY 1-1
II. PHYSICAL AND CHEMICAL PROPERTIES'.. - H-l
A. General Properties II-1
6. Manufacture and Use H-l
C. Environmental Fate and Stability II-1
1. Leaching From Soils II'1
2. Degradation in the Environment 11-3
D. Summary ^~?
III. TQXICOKINETICS III-l
A. Absorption III-l
B. Tissue Distribution III-l
C. Metabolism III-5
D. Excretion IH-5
•:-. ' E. Bioaccumulation and Retention , ..>• ...... MI-5
F. Summary 111-6
IV. HUMAN EXPOSURE IV'1
V. HEALTH EFFECTS IN ANIMALS V-l
A. Short-term Exposure V-l
1. Acute Toxicity V-l
2. Subacute Toxicity V-3
B. Long-term Exposure V-4
1. Subchronic Toxicity v~4
2. Chronic Toxicity V-6
C. Reproductive/Teratogenic Effects V-ll
D. Mutagenicity v~16
£. Carcinoyenicity V-17
F. Summary V-19
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TABLE OF .CONTENTS (continued)
Page
VI. HEALTH EFFECTS IN HUMANS VI-1
A. Clinical Case Studies . VI-1
B. Epidemiological Studies VI-1
C. High-Risk Populations VI-1
0. Summary VI-1
VII. MECHANISMS UF TUXICITY VII-1
A. Mechanisms in Animals VII-1
B. Mechanisms in Plants . VII-1
C. Interactions VII-1
D. Summary J • VII-2
VIII. QUANTIFICATION UF TUXICOLOGICAL EFFECTS . VIII-1
A. Procedures for Quantification of Toxicological Effects .... VIII-1
1. Noncarcinogenic Effects VIII-1
2. Carcinogenic Effects VI11-4
B. Quantification of Noncarcinogenic Effects for Dalapon .... VIII-6 a
1. Une-day Health Advisory VIII-6
2. Ten-day Health Advisory VIII-6
3. Longer-term Healtn Advisory ,.>.-;.. VIII-8
4. Reference Dose and Drinking Water Equivalent Level- .... VI11-11
C. Quantification of Carcinogenic Effects for Dalapon VIII-14
D. Existing Guidelines and Standards VIII-15
E. Summary VIII-15
IX. REFERENCES IX-1
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LIST OF FIGURES
Fiyure No. Page
II-l Major Metabolic and Degradative Routes of Dalapon II-6
vii
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LIST OF TABLES
Table No.
II-l
III-l
III-2
V-l
V-2
V-3
V-4
V-5
V-6
VIII-1
VI11-2
VIII-3
Page
Properties of Dalapon (2,2-Dichloropropionic Acid)
arid Its Salts II-2
Tissue Distribution of Dalapon in Dogs Given Daily
Oral Doses for 1 Year III-2
Tissue Distribution of Dalapon in Male and Female
Rats Receiving Dietary Dalapon for 2. Years III-4
Acute Oral LD5Q Values for Dalapon Sodium ....... V-2
Average Weights of Various Organs Taken From Dogs
Receiving Dalapon Sodium by Capsule for 1 Year ..... V-8
Average Weights of Various Organs Taken From Rats
Maintained for 2 Years on Diets Containing Dalapon
Sodium V-10
Selected Nonneoplastic Lesions Observed in Mice Fed
Dowpon M for 2 Years V-12
Summary of Results of Reproduction Study in Three ||
Generations (Two Litters Each) of Rats Fed Diets
Containing Dalapon Sodium . . • . .. , V-13
Selected Neoplastic Lesions Observed in Mice Fed-
Dowpon M for 2 Years
V-18
Summary of Candidate Studies for Derivation of the
Longer-term Health Advisory for Dalapon VIII-9
Summary of Candidate Studies for Derivation of the
DWEL for Dalapon VIII-12
Summary of Quantification of Toxicological Effects
for Dalapon VIII-16
viii
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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 (HCLGs) and promulgate National Primary Drinking
Water Regulations for each contaminant, which, in the judgment of the
Administrator, may have an adverse effect on public health and which is known or
anticipated to occur in public water systems. The HCLG 1s 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 HCLG 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 were 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 was 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 April 1987; however, more recent
data have been added during the review process and in response to public
comments.
When adequate health effects data exist, Health Advisory values for less-
than-lifetime exposures (One-day, Ten-day, and Longer-term, approximately 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.
James R. Elder
Director
Office of Ground Water and Drinking Water
Tudor T. Davies
Director
Office of Science of Technology
ix
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I. SUMMARY
Dalapon Is a herbicide used to control grasses in a wide variety of crops
and in a number of noncrop applications, such as along drainage ditches and
railroads and in industrial areas. It is an organic acid (2,2-dichloropropionic
acid) soluble in water, metnanol, and ethanol, and is marketed as the sodium salt
or as a mixture of the sodium and magnesium salts. In the environment, it is
rapidly degraded in soils by a variety of microorganisms. The major degradation
product, pyruvic acid, is a normal intermediate in the metabolism of plants and
animals.
The absorption of dalapon from the gastrointestinal tract of mammals has
not been measured directly. However, on the basis of excretory data in dogs
and humans, it appears that dalapon is relatively well absorbed (at least 50%).
Studies in dogs and rats indicate that orally ingested dalapon is distributed
to "most" tissues of the body (kidney>liver>muscle>brain>fat), with no marked
preferential accumulation in any one tissue. In dogs, 65 to 70% of an oral
dose (500 mg/kg) is excreted in the urine (as unchanged dalapon) within 48
hours, in numan subjects, approximately 50% of five consecutive daily doses
of 0.5 mg/kg of dalapon sodium was excreted in the urine within an 18-day
%
period.
Acute toxicity data indicate that dalapon has a low order of toxicity in
mammals, witn a range of 1^50 values of 4 to 9 g/kg. The dry powder or a concen-
trated solution can be irritating to the eyes or skin if not removed by washing.
Short-term multiple dose studies suggest that the toxicity of the compound is
not cumulative. Cattle that received a 1-g/kg daily oral dose for 10 days
showed some signs of toxicity but rapidly recovered when dosing ceased. Slight
1-1
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cloudy swelling of the convoluted tubules and hypertrophy or swelling of the
glomerular cells of the kidney were the only findings in a bull calf receiving
1 g/kg/day. Dogs were dosed by gavage for an 81-day period, initially with 50
tny/kg/day, with dosages adjusted upward until the animals were receiving 1,000
mg/kg/aay. Vomiting ensued at this high dose level, and the study was terminated
at 81 days. Except for vomiting, no other signs of toxicity were evident.
Extensive hematological and biochemical parameters were all normal, as were the
organ-to-body weight ratios.
In a 97-day rat study, there were no effects in male rats fed dalapon in
the diet at dosage levels up to 115 mg/kg/day. In female rats, there were
slight, statistically significant increases in average kidney weights at the •
34.6 mg/kg/day level. At doses of 346 or 1,150 mg/kg/day, both male
and female rats showed growth retardation, increased liver and kidney weights,
and slight histopathological changes in the liver and kidneys. This study
establishes a No-Observed-Adverse-Effect Level (NOAEL) of-11.5 mg/kg/day for
oral intake in the rat.
In a 1-year study with mongrel dogs, significant increases were observed
in the average kidney weight in dogs receiving 100 mg/kg/day but not in those
receiving 50 mg/kg/day. All other parameters were comparable to controls. In
"a 2-year rat study, significant increases were noted in the kidney weight in
rats receiving 50 mg/kg/day, but not in those receiving 15 or 5 mg/kg/day. In
this chronic study, a dose of 15 mg/kg/day is identified as the NOAEL. In a
2-year mice study, increased liver weights were noted at 200 mg/kg/day Dowpon
M in the diet. No associated lesions were noted upon histologic examination
of the livers.
1-2
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There were also increased incidences of benign lung adenomas and cystadenomas j|
of the harderian gland in male mice fed dalapon for 2 years. No tumors were
found in rats fed dalapon for 2 years.
In a three-generation reproduction study in rats, no reproductive effects
were found in rats administered dalapon in the diet at levels up to 3,000 ppm
(15U nig/kg/day). In a rabbit teratogenicity study, decreased body weights
were noted in pups from dams receiving oral doses of 300 mg/kg/day. However,
no fetal effects were noted at 30 or 100 rag/kg/day. Similarly, the mean of the
pup weights was depressed when pregnant female rats received 1,000 or 1,500
mg/kg/day in the diet from days 6 through Ib of gestation but not wnen they
received 500 mg/kg/day. No other effects on tne fetuses were observed.
Dalapon was not mutagenic in a variety of organisms including Salmonella
typhimurium, Escherichia coli, T4 bacteriophage, Streptomyces coelicolor,
Saccharomyces cerevisiae, and AsDergil_lu,s_ nidulans. In one study (technical
details not provided), dalapon was found to increase chromosomal aberrations in
mice at doses of 2UU mg/kg or more.
No reports of adverse effects in individuals who manufacture or utilize
dalapon were found. In addition, no human toxicity data or epidemiological
studies were found for this compound.
In liver mitochondria, dalapon exerts a mild inhibition of pyruvate uptake.
In plant tissues, dalapon has been found to inhibit several enzyme systems that
utilize pyruvate. The role of enzyme inhibition in the herbicidal activity of
dalapon is not clear.
No acute oral exposure data were found that were suitable for calculation
of a One-day Health Advisory (HA). A maternal NGAEL of 30 mg/kg/day, based on
1-3
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a teratogenicity study in rabbits, was selected to calculate the Ten-day HA of
3000 ug/L for a 10-kg child. This value is considered to be appropriate as a
conservative estimate of the One-day HA value for a 10-kg child as well. A
NOA£L of 15 mg sodium dalapon/kg/day, based on a 2-year feeding study in
rats, was used to calculate a Longer-term HA of 300,ug/L for a 10-kg child and
9UO jjg/L for a 70-kg adult. The same study was also used to calculate a
Reference Dose (RfD) of 27 ug/kg/day ahd a Drinking Water Equivalent Level
(DWEL) of 900 ug/L for a 70-kg adult. (All the Health Advisory, RfD and DWEL
values were referring to the active ingredient dalapon acid). No sensitive
subpopulations or other special considerations are recognized regarding the risk
of dalapon exposure.
1-4
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II. PHYSICAL AND CHEMICAL PROPERTIES
A. GENERAL PROPERTIES
Dalapon (2,2-dichloropropionic acid) is a carboxylic acid that is soluble
In water, methanol, and ethanol. The chemical and physical properties of
dalapon are shown in Table II-l.
B. MANUFACTURE AND USE
Dalapon formulations are registered for selective use in controlling
grasses in a wide variety of crops, including specified fruit trees, beans,
coffee, corn, cotton, peas, beets, and sugarcane. It is also registered for
use in noncrop areas such as lawns, industrial areas, ditches, and along rail-
road tracks. Dalapon is marketed as the sodium salt or as a mixture of the
sodium and magnesium salts (Kenaga, 1974).
C. ENVIRONMENTAL FATE AND STABILITY . --.;. • • ...."
1. Leaching From Soils
Since botn dalapon and its salts are water soluble, they tend to follow
waterflow in the environment. Warren (1954) reported that dalapon was readily
leached from four types of soil. Smith et al. (1972) studied the leaching of
dalapon in a soil column (8.5-inch) of sandy loam. Dalapon was present at a
level of application of 1 Ib/acre. Nine acre-inches of water applied in
O.b-inch increments leached 99.4% of the dalapon from the column. On the basis
of soil tnin-layer chromatography (TLC) of 40 different pesticides, Helling
(1971) classified dalapon in the group with the greatest mobility.
II-l
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Table II-l. Properties of Dalapon (2,2-Dichloropropionic
Acid) and Its Salts
Property
Value
Physical appearance
Acid
Sodium salt
Magnesium salt .
Melting point
Sodium salt
Magnesium salt
Molecular weight
Acid
Sodium salt
Magnesium salt
Density
Solubility (g/lUO 9 solvent)
Water ' '""
Methanol
Ethanol
Partitioning coefficient
• (n-octanol/water)
pKa
Colorless liquid
White solid
White-tan solid
Decomposes at 193 to 197°C
Decomposes at 193°C
143
165
308.5
1.389 g/mL
Acid Na salt
>80.0
18.5
82.7
5.?a
1.74
90.0-
17.9
<18.5
Mg salt
>80.0
35.9
. 25.5
Taken from Kenaga (1980).
SOURCE: Adapted from Kenaga (1974)
II-2
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Miller and Uetzendaner (1973) sampled soils taken from a number of areas
of the United States at various time intervals up to 1 year after the applica-
tion of dalapon. At one sample site, no residues were found in the top 6
inches of soil after 40 days, regardless of the rate of application. At another
site, residues of dalapon in the top 6 inches of soil after 7 days were 2.0 to
2.2 ppm; at 14 days, 0.11 to 0.28 ppm; at 28 days, 0..06 ± 0.15 ppm; and at 42
days, <0.025 ppm. No dalapon at any site was detected in the 6- to 12-inch
soil layer. Thus, although dalapon moves rapidly in the environment, it appears
that it is.also rapidly degraded.
Oalapon was found in one of the surface water or ground water samples
analyzed from 14 samples taken at 14 locations (STORE!, 1987).
2. Degradation in the Environment
The sodium salt of dalapon hydrolyzes slowly in water to produce pyruvic
acid arid chloride ion; the rate of hydrolysis .increases with increasing tempera-
ture. After 175 hours, the extent of hydrolysis at 25°C for 1, 5, and 18%
dalapbn solutions was U.41, 0.61, and 0.8%, respectively (Brust, 1953).
Hydrolysis of solutions of either dalapon or dalapon sodium salt is accel-
erated at alkaline pH. For example, hydrolysis of dalapon sodium salt at 60°C
was 20% complete in 30 Hours, at which time the equilibrium pH was 2.3. In
contrast, hydrolysis was 50% complete in 30 hours when the pH was maintained at
12 during the study (Tacey and Bellinger, 1958). Photodegradation of dalapon
to pyruvate may also occur, and the pyruvate may then be further converted at a
slower rate to acetaldehyde and carbon dioxide (Tanaka and Wien, 1972).
Although laboratory studies indicate that dalapon is a highly mobile
compound {Warren, 1964; Helling, 1971, Kenaga, 1974) and should be readily
II-3
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Teachable from soils, field data show that under many practical conditions
dalapon does not get below the top 6-inch layer of soil. This is probably
because microbial action proceeds at a faster rate than leaching under favor-
aole conditions (Kenaga, 1974). Microbial degradation is by far the most
important process affecting the fate of dalapon in soil. Other processes,
which are of lesser importance, are leaching and runoff, chemical degradation,
adsorption, and volatilization. Kenaga (1974) indicated that photodegradation
may not be a major degradative pathway in the environment. Based on the light
absorption characteristics of aqueous solutions of sodium salts of dalapon,
photodecomposition of dalapon in field applications is improbable (Kearney et
al., 1965).
Microbial degradation in soil has been well estaolished. Thiegs (1955)
found that the concentration of dalapon (59 ppm) in autoclaved soil did not
change after incubation at 100°F for 1 week, whereas in nonautoclaved soil
dalapoh disappeared in 4 to -5 weeks after one application of 50 ppm and in 1
week after a second application.
A laboratory study (Holstun and Loomis, 1956) showed that dalapon degrada-
tion in soil was very sensitive to temperature. Little.or no degradation .
occurred wnen soil temperature was below 15°C, but decomposition at a concentra-
tion of 120 ppm (12 mg/kg) in soil was essentially complete (<15 ppm) after 2
weeks at 30°C. The rate of degradation was inhibited by lack of moisture, low
pH, and tne addition of large quantities of organic matter, suggesting that
bacterial decomposition of dalapon was taking place. Jensen (1957) found a
group of bacteria that decomposed dalapon in soil after an initial incubation
period of 4 weeks. Magee and Colmer (1959) found eight species of soil
bacteria that, when grown on agar plates, were able to decompose up to 5,QUO
II-4
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ppm dalapon. Six of these were tentatively identified as Agrobacter and two as
Pseudomonas; however, other unidentified bacteria, molds, and actinomycetes
were also present.
Hirsch and Alexander (1960) found that 89 to 100% of the chlorine in
dalapon was released in 3 weeks by soil cultures of Nocardia and Pseudomonas
microorganisms. In laboratory tests, decomposition of 50 ppm dalapon in
California soil samples ranged from complete disappearance in 2 weeks to one-
third disappearance in 8 weeks {Day et al., 1963). The degradation of dalapon
in these soils was unrelated to soil type, texture, cation exchange capacity,
or total organic matter, but evidently was related to the various microbial
populations in the samples. Kaufman (1964) reported that under greenhouse
conditions, dalapon disappeared in 4 to 8 days in muck soil, in 8 to 16 days in
loam and silty loam soils, in 16 to 32 days in sandy loam soil, and in 32 to 64
days in silty clay soil. This appeared to be primarily a consequence of bac-
terial degradation, although other soil microorganisms were present.
Kearney et al. (1964) identified the following microbial genera capable of
liberating chloride ion from dalapon: Pseudomonas, Bacillus, Alcaligenes,
Agrobacterium, Arthrobacter, and Nocardia. A suspension from an Arthrobacter
species, presumably containing only free enzymes, was also capable of
denalogenating organically bound chlorine from dalapon and converting dalapon
to pyruvaze. Foy (-1961) identified monochloropropionate as a degradation
product of dalapon in a stock solution contaminated by a fungus that was
not identified.
A summary of degradative reactions of dalapon in the environment is shown
in Figure II-l. The major degradation product, pyruvic acid, and its breakdown
products are all normal metabolic intermediates in mammalian metabolism.
II-5
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fungi
CH3CC12COOH*
Dalapon
mlcrobial
hydrolysis
CH3CHC100H*
alpha-Chloropropionic
acid
[CH3CC10HCOOH]
phocodegradation
[CH3CC1COOH]
CH3COCOOH* + CV
Pyruvic acid
Energy cycles of
cells (Krebs, lactic
acid, etc.)
CH-CHO + C02
Acetaldehyde
I
CH^COOH*
Acetic acid
I
Figure II-l. Major metabolic and degradative routes of dalapon. (Starred
acids will be in equilibrium with their anions, with the position
of the equilibrium depending on pH and the specific cations in a
particular environment, and the compounds in brackets will be
transient.)
SOURCE: Adapted from Kenaga (1974).
II-6
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D. SUMMARY
Dalapon (2,2-dichloropropionic acid) is a herbicide that is commercially
available as formulations of the sodium and magnesium salts. It is utilized
to control grasses in crops, drainage ditches, along railroads, and in indus-
trial areas. Dalapon is water soluble and tends to follow waterflow. In the
environment, it is rapidly degraded in soil by a variety of microorganisms.
The major metabolic product, pyruvic acid, may be further degraded to yield
acetaldehyde and acetate. These degradative products are normal intermediates
in mammalian metabolism.
II-7
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III. TOXICOKINETICS
A. ABSORPTION
No direct data on the absorption of dalapon were found in the literature.
leasure (1964) reported that dalapon fed to animals is quickly excreted in the
urine, but no data were provided. Hoerger (1969) found that 65 to 70% of an
oral dose (5UU mg/kg) administered to dogs was excreted in the urine within 2
days, and that humans ingesting 0.5 mg/kg of dalapon sodium on each of 5 con-
secutive days excreted approximately 50* in the urine over the subsequent
18-day period. These results indicate that dalapon is well absorbed from the
gastrointestinal (GI) tract of animals and humans.
B. TISSUE DISTRIBUTION
Paynter et al. (1960) reported on the tissue distribution of dalapon in
dogs receiving 0, 15, 50, or 100 mg/kg/day of dalapon sodium. Twelve mongrel
dogs were divided into four groups of two males and one female per group. The
\
compound was administered by capsule, 5 days a week for 52 weeks. Body weight
was recorded weekly. Food was offered once a day, and water was available
ad libitum.
At termination of the study, the dogs were necropsied, tissues were imme-
diately frozen at dry-ice temperature, and then kept at 0°C or below until
analyzed. Dalapon was extracted and measured by the method of Smith et al.,
(1957). Tissue distribution data are shown in Table III-l. No consistent sex
differences were noted in the distribution of the compound in the tissues
examined. The pattern of tissue distribution was kidney>liver>muscle>brain>fat,
III-l
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Table III-l. Tissue Distribution of Dalapon in Dogs
Given Daily Oral Doses for 1 Year
Tissue
Kidney
Liver
Muscle
Brain
Fat
Sex
M
F
M
F
M
F
M
F
M
F
15
b
23
17
- 27
17
15
12
11
7
2
1
Dosage (mg/kg/day)
50
21
32
16
27
13
27
9
13
2
4
a
1UU
78
60
48
57
51
35
25
18
15
5
aOral dose of dalapon sodium, 5 days/week.
DData are expressed as mg 2,2-dichloropropionic acid per kg tissue,
SOURCE: Adapted from Paynter et al. (1960).
III-2
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In a related study, Paynter et al. (1960) reported on the analysis of
tissue from rats maintained for 2 years on a diet containing dalapon at several
different dosage levels. Four groups of 24 male albino rats, Carworth Farm
strain, received dalapon sodium in their diet at levels of 0, U.01, 0.03, or
u.1%, approximating 0, 5, 15, or 50 mg/kg/day, respectively, according to the
authors. At termination of the study, tissues were immediately removed, frozen
at dry-ice temperature, and kept frozen until analyzed. The tissue distribution
in male and female rats after 2 years on diets containing dalapon is shown in
Table III-2. The pattern of distribution was similar to that seen in dogs
(i.e., kidney>liver>rauscle>brain>fat); no dalapon was detected in the muscle,
brain, fat, and milk at the low dose. Dalapon has also been detected in the
milk of lactating female dogs given dalapon for an unspecified length of time
(Dow, 1962b). Samples of milk were collected, frozen, and then analyzed by gas
chromatography with electron-capture detection. The concentrations found were
10.1 and 11.5 ppm in the milk of dogs at the 50-mg/kg dose level and 15.1. ppm
in dogs at the 100-mg/kg level.
Fertig and Schreiber (1961) studied dalapon levels in cow's milK. Dairy
cattle (6 Jerseys, 16 Holsteins, 6 Guernseys, and 6 Brown Swiss) were fed
dalapon at a level equivalent to 300 ppm in the diet (corrsponding to about 9.0
>,
my/kg/day). The dalapon was mixed with a grain concentrate and fed just prior
to milking. The total study period included 1 week of standardized prefeeding,
3 weeks of dalapon feeding, and 1 week of postdalapon feeding. Duplicate milk
samples were taken morning and evening from each cow and analyzed for dalapon
by the method of Kutschinski (1961). Milk levels reached maximum at about 7
days and remained essentially constant (1.08 to 1.46 mg/kg) over the total
3-week feeding period. There were no differences in response among the four
breeds.
III-3
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Table III-2. Tissue Distribution of Dalapon in Hale and Female Rats
Receiving Dietary Dalapon for 2 Years
Tissue
Kidney
Liver
Muscle
Brain
Fat
Milkc
Dosage (mg/kg/day)a
5 15
4.0° 9.7
1.0 . 3.5
2.9
- - 2.6
0.5
6.0
50
28.2
10.7
7.5
5.4
1.4
19.1
aEstimated by the authors from dietary levels of 0.01, 0.03, and 0.1%.
bData are expressed as mg 2,2-dichloropropionic acid per kg tissue.
cFrom third-generation lactating females; milk level in rats maintained on
diets containing 3,000 ppm (150 mg/kg) was 29.3 mg/kg.
SOURCE: Adapted from Paynter et al. (1960).
III-4
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C. METABOLISM
Leasure (1964) found that 65 to 70% of a single oral dose of 500 mg of
dalapon sodium administered to dogs was excreted unchanged in the urine within
48 hours. Redemann and Hamaker (1959) reported that in a cow fed 36C1 -labeled
dalapon, only two labeled products were found in the milk. These were dalapon
and chloride ion, indicating that dehalogenation of dalapon had occurred to
some extent in the cow. No further details of this study were available.
D. EXCRETION
Hoerger (1969) fed a single oral dose (500 mg/kg) of dalapon sodium to
dogs. The animals excreted 65 to 70% of the dose in the urine as unchanged .
dalapon within 48 hours. When the animals were fed repeated daily doses of 50
or 100 mg/kg for a 611-day period, total recovery of dalapon in the urine ranged
from 25 to 53%. Hoerger (1969) also studied dalapon excretion in human sub-
jects who consumed five successive daily oral doses of 0.5 mg/kg- of dalapon
sodium. Approximately 50% of the dose was found in the urine over the subse-
quent 18-day period. No other studies of the excretory rate for dalapon were
found in tne literature.
E.
BIOACCUMULATION AND RETENTION
No studies were found that 'provided direct estimates of half-lives of.
dalapon in oody tissues. However, the long-term studies by Paynter et al .
(I960) (see Section II. 8, Distribution) indicate that there is no significant
accumulation of dalapon in tissues of either dogs or rats after 1 to 2 years of
exposure at doses ranging from 5 to 100 mg/kg/day. Fertig and Schreiber (1961)
found that in dairy cattle receiving 9.0 mg/kg/day, dalapon levels reached a
steady-state level (1.08 to 1.46 mg/kg milk) in 7 days, and this did not
III-5
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Increase over a period of 3 weeks. When dalapon feeding was discontinued, milk ||
levels decreased to 0.115 mg/kg in 3 days and to 0.045 mg/kg in 7 days. Resi-
dues in tissues were not investigated.
F. SUMMARY
Few studies of dalapon toxicokinetics were found in the literature. On
the basis of excretory data in dogs and humans, it appears that dalapon is
relatively well absorbed when ingested orally (at least 50 to 70%}. Tissue
distribution studies in dogs and rats show that orally ingested dalapon
distributes to most tissues of the body (kidney>liver>muscle>brain>fat), with
no marked preferential accumulation in any one tissue. In dogs, 65 to 70% of
an oral dose (500 mg/kg) is excreted in the urine (as unchanged dalapon) in 48
hours. In human subjects, it was found that approximately 50% of five consecu-
tive daily doses of 0.5 mg/kg of dalapon sodium'is excreted in the urine within
an 18-day period.
III-6
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IV. . HUMAN EXPOSURE
This section will be provided by the Science and Technology Branch, ODW,
EPA, at a later date.
IV-1
I
1
-------
V. HEALTH EFFECTS IN ANIMALS
A. SHORT-TERM EXPOSURE
1. Acute Toxicity
Paynter et al. (I960) studied the acute oral toxicity of dalapon sodium
in rats, mice, guinea pigs, rabbits, and chicks. The technical-grade 'material
used in the acute studies contained 83 to 85% dalapon sodium salt; 6% related
chloropropionic acid, sodium salt; 1% pyruvic acid sodium salt; 8% sodium
chloride; and 2% unidentified. The animals were administered single doses of
dalapon ranging. from 1,000 to 15.80U rug/kg body weight. The acute oral LDsg
values were calculated for the five species by tne "Moving Average" method of
Thompson (1947), and the results are shown in Table V-l; The acute oral LDgQ
values for these five species ranged from 3,860 mg/kg for the female rabbit and
female guinea pig to 9,330 mg/kg for the male rat.
Kochkin (1967) reported that the acute oral LDso value of dalapon sodium
was 7,100 mg/kg for the albino mouse and 4, 700. mg/kg for the white rat. These
values are vary similar to those reported by Paynter et al. (1960). As part of
a study of 57 pesticides, Gaines and Linder (1986) determined the dermal LDsg
value of dalapon applied in aqueous solution to be greater than 5,000 mg/kg in
botn male and female Sherman rats, and the oral LDso to be 7,126 mg/kg in males
and 6,936 in females.
Very slight dermal toxicity was observed in rabbits treated with concen-
trated solutions of dalapon (Paynter et al., 1960), and no dermal effects were
observed in a calf, hog, or in three sheep treated with dalapon spray (Goldstein
and Long, 1960). Slight to moderately severe cornea! injury and conjunctiva!
irritation were observed in rabbits treated with dalapon powder or 10% dalapon
V-l
-------
Table V-l. Acute Oral LDsg Values for Dalapon Sodium
Species
Rat
Mouse
Guinea pig
Rabbit
Chick
Sex
M
F
N/S
M
F
N/S
F
F
F
M/F
LD50 (mg/kg)
9,330
7,570
4,700
7,126
6,936
7,100
>4,600
3,860
3,860
5,660
Reference
Paynter et al .
Kochkin (1967}
(1960)
Gaines and'linder (1986)
Kochkin (1967)
Paynter et al .
Paynter et al .
Paynter et al.
Paynter et al .
(1960)
(1960)
(I960)
(1960)
V-2
-------
solution, but these effects were diminished by washing the eye and were fully
reversible (Paynter et al., 1960).
2. Subacute Toxicity
i
Paynter et al. (1960) intubated a heifer (weighing 252 kg) and a bull
suckling calf (weighing 59.1 kg) with 1.0 g/kg of dalapon, sodium dissolved in .
water on each of 10 consecutive days. , During the latter part of the study, the
heifer showed signs of general lassitude, diarrhea, roughness of coat, loss of
appetite, slight loss of weight, slowed pulse rate, mild cyanosis of the mucous
membranes, and some discharge from the eye. Four days after the last dose, the
heifer appeared to have recovered and was in good condition. The slowed pulse
rate was still present, and some discharge from the eyes remained. At this
time, the animal was sacrificed and necropsied. During the course of the
study, the nursing bull calf showed no signs of toxicity and gained 6.8 kg in
weignt. Twenty-four hours after the last dose, the calf was sacrificed and..
necropsied. Sections of the rumen, reticulum, omasum, abomasum, lymph nodes,
adrenals, tnyroid, heart, kidneys, liver, spleen, pancreas, lung, bladder, and
gallbladder of both animals appeared normal on microscopic examination. Tne
kidneys showed slight cloudy swelling of the convoluted tubules and hypertrophy
or swelling of the glomerular cells with decreased glomerular spaces.
Palmer and Radeleff (1964) reported the effects of feeding commercial
dalapon sodium to sheep, predominantly of the Delaine breed, and a mixed dairy
breed of cattle (one animal per dose level). No apparent effects were noted in
the sheep receiving 10 daily doses of 250 or 500 mg/kg or in the cattle
receiving 10 daily doses of 250 mg/kg or 8 daily doses of 5UO mg/kg. However,
parotid swelling was observed in the cow receiving 500-mg/kg/day doses. No
V-3
-------
control animals were used. One sheep was continued on a chronic regimen of 481
daily doses of 100 my/kg with no signs of toxicity reported.
B. LONG-TERM EXPOSURE
1. Subchrom'c Toxicity
Kochkin (1967) reported the results of a 2-mbnth dietary study in albino
rats. Two dose levels (one-twentieth and one-fifth of the LDsg) were employed
(equivalent to 235 and 940 mg/kg/day, on the basis of the LDgo of 4,7UO mg/kg
reported by the author). The following parameters were studied: blood count,
prothrombin time, whole blood catalase and cholinesterase activity, serum -SH
levels, tissue respiration, weights of internal organs, vitamin C content of
adrenals, and the -SH content of homogenized liver. No details of methods were
provided. None of the animals died during the 2-month feeding period, although
the animals receiving 940 mg/kg/day had decreased weight gain. Tnis group also
nad decreased serum -SH levels (p <0..002) and increased.organ-to-body weight - .
ratios for liver, kidney, spleen, thyroid, pituitary, and adrenals. Tnere was
"irregular thickening of the stomach submucosa due to edema, swelling of the
basal cells and inflammatory cellular infiltration. In the lumen of the small
intestine there was profuse desquamation of the glandular epithelium and defor-
mation of the papules, due to infiltration by inflammatory-cellular elements."
No histological changes were reported in other organs.
Paynter et al. (1960) maintained groups of 10 male and 10 female rats
(Wistar-Dow strain) for 97 days on diets containing 0.0, 0.0115, 0.0346, 0.115,
0.346, or 1.15% dalapon sodium. These dosages are equivalent to 0.0, 11.5,
34.6, 115, 346, or 1,150 my/kg/day, respectively, according to the authors. No
effects were found in male rats ingesting up to 115 mg/kg/day. In female rats,
V-4
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there were statistically significant increases (no p value given) in average
kidney weights at the 34.6- and 115-rag/kg/day dose levels, but no other differ-
ences from the controls. No histopathological changes were found that correlated
with the increased kidney weights. Toxic effects were noted at the higher doses
(346 and 1,150 mg/kg/day), including growth retardation, increases in average
weight of the liver and kidneys, and slight histopathological changes (not
specified) in the liver and kidneys of both sexes. There were no dose-related
changes in mortality, food consumption, hematological data, average body weights,
or microscopic lesions of the spleen, lung, or heart. An NOAEL of 11.5 mg/kg/day
was identified, based on increased kidney weights in females rats receiving
3.4.6 mg/kg/day.
Paynter et al. (196U) administered dalapon sodium orally by capsule to
one male and one female mongrel dog, 5 days/week for 80 days. Dogs were weighed
weekly, and doses were adjusted for weight gain. During the first 2 weeks,
.each dog received a dose containing bO mg/kg/day dalapon;sodium. The dose was
then adjusted upward weekly until a maximum of 1,000 mg/kg was reached. During
the 10th and llth weeks, the dose was divided into two 500-mg daily doses in an
attempt to prevent vomiting. The following parameters were monitored both
prior to and at termination (day 81) of the study: complete blood counts, cell
volumes, blood urea nitrogen (BUN), bromsulphalein (8SP) liver function tests,
and urinalyses. At 81 days, the animals were killed and necropsied. Gross
examination revealed no specific findings in either dog that appeared to be
compound related. Organ-to-body weight ratios of the liver, kidneys, spleen,
and testes for both dogs were within normal limits as were hematological and
biochemical measurements. Since only two animals were used in this study,
increasing doses were administered during the study, and no control animals
were included, the toxicological effects could not be adequately assessed.
No NOAEL or LOAEL was identified.
V-5
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Kochkin (1967) administered perorally to albino rats, at 1, 10, and 200
mg/kg, dalapon sodium in aqueous solution six times/week for 5 months. The
number of animals and sex, weight, and strain of rats were not given. After 4
months, the serum -SH levels were depressed in the 200-mg/kg dose group
(p <0.05), while a decrease occurred in the 10-mg/kg dose group after 5 months
on the diet (p <0.01), Animals at the 10-mg/kg dose level also showed a slowing
of conditioned reflexes. During the fifth month, the frequency of cessations
of the conditioned reflexes and the number of phasic reactions increased
(p <0.01}. There was an increase in the organ-to-body weight ratio of the
thyroid of rats at the 2UO-mg/kg level. Microscopic examination of the thyroid
of the animals in this group showed marked vasodilation and hyperemia, which
the authors considered to be effects of dalapon. This effect was not noted 10 ._
the 10-mg/kg dose level animals. No effects were reported in the 1 mg/kg group.
Very few details on the methods including the number, sex, and strain of animals
used as well as results were reported for this study (Russian translation).
Therefore, the importance of the effects noted could not be adequately assessed--
and a NOAEL was not identified.
2. Chronic Toxicity
Paynter et al. (1960) studied the long-term effects of dalapon sodium in
mongrel dogs. Twelve healthy mongrel dogs were divided into four groups of
two females and one male per yroup. Each group received either 0, 15, 50, or
100 mg/kg/day of dalapon sodium administered by capsule, 5 days a week for
52 weeks. The following parameters were monitored for each dog initially and
at weeks 13, 26, and 52: complete blood count, BUN level, BSP liver function
test, and urinalysis. At necropsy, the heart, lungs, liver, spleen, kidneys,
and testes were weighed. Sections from the thyroid, lungs, heart, liver,
kidneys, adrenals, pancreas, spleen, lymph nodes, bone marrow, urinary bladder,
V-6
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and gonads of each animal were examined microscopically. All dogs showed
normal behavior, gained weight, and exhibited no evidence of adverse effects
attributable to the compound. There were no significant alterations in the
nematological or biochemical parameters. Average organ-to-body weight ratios
were essentially normal, except for a statistically significant increase
{p <0.05) in average kidney weight in the dogs that received 100 mg/kg/day.
The organ-to-body weight ratios are shown in Table V-2. Histopathological
examination of tissues showed no abnormalities, even in the heavier kidneys
from the high-dose group. A NOAEL of 50 mg/kg/day based on increased kidney
weights at 10U mg/kg/day was identified.
Paynter et al. (I960) also carried out a 2-year feeding study in albino
rats (Carworth Farm strain) given levels of 0.01, 0.03, and 0.1% dalapon sodium
in the diet. The authors calculated these dietary levels to approximate 5, 15,
and 50 mg/kg/day, respectively. Groups of 24 male rats were fed at each dose
level; groups of 20 female rats were fed at all but the 0.1%. level. Complete ...
blood counts and hemoylobin determinations were carried out on animals from
each group at the following intervals: initially, five males and five females;
at 14 weeks, three males and three females; at 26 weeks, two males and two
females; at 52 weeks, three males and three females; and at 104 weeks, three
males and three females. Interim sacrifices and histological examination were"1
performed at 26 weeks on two male and two female rats from each group and at 52
weeks on two males from each group. At 104 weeks, the remaining animals were
sacrificed and necropsied, and appropriate tissues were taken for histological
examination from representative-males and females from each group (number not
specified).
Growth, food consumption, survival, and hematological findings were compar-
able for dalapon sodium-treated male and female rats as compared to controls.
V-7
-------
a
Table V-2. Average Weights of Various Organs Taken from Dogs
Receiving Dalapon Sodium by Capsule for 1 Year
Dosage
(nig/kg/day)
Control
15
50
100
Weight
(kg)
9.33
+0.82
9.87
±1.85
8.43
+1.79
9.60
+1.21 •
Lungs
(%)
0.67
+0.12
0.70
+0.18
0.62
+0.06
0.73
.+0.15
Heart
(%)
0.64
+0.05
0.77
+0.07
0.88
j+0.23
0.85
+0.22
Liver
(%)
2.51
+0.22
2.91
+0.24
2.80
+0.09
2.83
+0.15
Spleen
(*)
0.15
±0.02
0.20
±0.03
0.20
+0.07
0.23
±0.05
Ki dneys
(*)
0.42
+0.03
0.43'
+0.02
0.46
+0.01
0.56
+0.03
Testes
(%)
0.17
±°-03
0.16
jKI.OO
0.18
+Q.OQ
0.21
+0.00
a
As percent of terminal body weights +_ SO.
SOURCE: Adapted from Paynter et al. (1960)
V-8
-------
The average kidney weight of the'male rats receiving the 5U-mg/kg/day dose
showed a statistically significant increase (p <0.05) as compared to the male
controls at the end of the 2-year period (Table V-3). Microscopic evaluation
of the tissues revealed no evidence of adverse effects. At dietary levels of 5
and 15 mg/kg/day, all parameters measured were comparable to controls. A NOAEL
of 15 mg/kg/day was identified for this study.
In a chronic dietary study conducted by Dow Chemical Company (1983),
groups of BSCSF^ mice (96 control/sex and 50/sex in each treatment group) were
fed Dowpon M (a mixture of 72.1% 2,2-dichloropropionate, sodium salt, and
13.8% 2,2-dichloropropionate, magnesium salt) at levels equivalent to 0, 2, 60,
or 2UU mg/kg/day for 24 months. An additional 10 animals of each sex were
maintained on the same treatment regimen and sacrificed after 12 months on the
diets. The parameters studied included mortality, clinical signs of toxicity,
body weight, food consumption, clinical chemistry, hematology, urinalysis,
gross pathology, organ weights, and histopathology. -At the 1-year interim-
sacrifice, a slight, nonsignificant increase in liver weights was observed in
the nigh-dose group (2UO mg/kg/day). Histological examination of the liver did
not reveal any lesions associated with the weight increase.. Red blood cell
(RBC) count, hemoglobin, and packed cell volume were significantly elevated
(p <0.U5) in all males in the treatment groups when compared to controls, but
the increases were not dose related. At the 2-year terminal sacrifice, the
slight increase in liver weight still persisted in the high-dose group.
Elevations in RBC count, hemoglobin, packed cell volume, and serum glutamic-
pyruvic transaminase (SGPT) for males in the high-dose group were attributed by
the authors to a disproportionate number of hepatocellular carcinomas in the
10 high-dose males sampled. However, the total numbers of liver tumors in the
treated groups were not significantly different from that of the control group.
V-9
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Table V-3. Average Weights of Various Organs Taken From Rats Maintained
for 2 Years on Diets Containing Dalapon Sodium
Dietary
Level (%)
Control
0.01
0.03
0.10
Control
0.01
0.03
Number
Sex of rats
M 15
M 16
M 15
M 15
F 12
F 15
F 13
Body
weights (g)
488
±60
491
±65
463
±94
473
±58
336
±39
326
±66
353
±64
Liver (%)
2.88
• ±0.37
2.79
±0.38
2.59
±0.33
2.91
±0.25
3.54
±0.46
3.35
±0.43
. 3.51
±o.io
Kidneys (S)
0.64
±0.06
0.66
±0.10
. 0.68
±0.14
0.71*
±0.20
0.68
±0.09
0.80
±0.27
0.70
±0.14
Testes {*)
0.73
±0.10
0.64
±0.15
0.60
±0.15
0.69
±0.10
—
--
—
a
As percent of terminal body weights ± SD.
*Significantly different from controls at p <0.05.
SUURCE: Adapted from Paynter et al. (1960).
V-lu
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The clinical chemistry and heraatology parameters were comparable between control
and high-dose females. It should be noted that the females from all groups
exhibited fibrous osteodystrophy (Table V-4), a diffuse bone disorder that
caused elevations in alkaline phosphatase values. There was also a significant
increase (p <0.05) in the incidence of extramedullary hematopoesis in the mid-
and high-dose females when compared to controls. The authors considered this .
to be coincidental and of no toxicological importance. An increase in the
incidences of benign lung tumors and cystadenomas of the harderian gland was
noted in the high-dose males but the increase was within the range of historical
controls and therefore, was not attributed to dalapon administration. A NOAEL
of 60 mg/kg/day was identified from this study.
C. REPRODXTIVE/TERATOGENIC EFFECTS
Paynter et al. (1950) carried out a three-generation reproduction study
in rats administered 0, 0.03, 0.1, or 0.3% dalapon sodium in the diet (approxi-
mately U, 15, 50, or 150 mg/kg/day, respectively). Groups of young albino rats
(4 males and 12 females; strain not specified) were started on the diets at 90
days of age. At 110 days of age, the animals were placed together in breeding
cages. The FQ generation and all descendent animals were maintained on the
dalapon sodium diets throughout the study. All tne pups from the F]a litter
were discarded, and the females were returned to the breeding cages after 10
days. The resultiny FIJJ litters were maintained on their respective diets for
selection of 4 males and 12 females to be mated when 110 days old to produce
the Fga and ?2b generations. This process was repeated to produce the subsequent
generation. Indices of fertility, gestation, viability, and lactation were
recorded, and these data are summarized in Table V-5. The data show that
dalapon sodium in the diet through three generations of two litters each had no
effect on reproduction parameters, even at dietary levels of 0.3% (3,000 ppm).
V-ll
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Table V-4. Selected Nonneoplastic Lesions Observed in Mice Fed Dowpon M for 2 Years
Dietary Level (mq/kg/day)
Males
Organ/Lesion
Liver
Aggregates of retlculo-
endothelial cells
Foci of altered hepatocytes
Soleen
Extramedullary hemato-
poiesis
Pancreas
Cyst
Bone
»—
fibrous osteodystrophy
Kidneys
luouiar atrophy, multi focal
Cortical cyst
Tubular dilation, multifocal
0
(86)a
28
2
(86)
10
(86)
2
(86)
0
52
9
4
2
(*0)
9 '
2
(50)
4
(50)
1
(50)
0
34
1
3
60
(bO)
15
2
(50)
3
(49)
0
(50)
0
28
0*
2
200
(bO)
15
4
(50)
11
(50)
1
(50)
0
27
1
5
0
. (85)
65
3
(86)
5
• (86)
1
(86)
75
5
0
1
Females
2
(t>Q)
27*
1
(50)
6
(50)
1
(50)
44
2
1
0
60
(=0)
35
2
(50)
9*
(49)
0
(50)
45
7
0
0
200
(DO.
33
1
(so;
ii'
(50
3
(50.
45
3
0
U
aNumbers in parentheses represent the number of tissues examined.
*Significantly different from controls at p <0.0b.
SOURCE: Adapted from Dow (1983).
V-12
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Table V-5. Summary of Results of Reproduction Study in Three Generations
(Two Litters Each) of Rats Fed Diets Containing Dalapon Sodium
Dietary
levels (%)
Control
0.01
0.1
0.3
Control
0.03
0.1
0.3
Control
0.03
0.1 .
0.3
Generati on
FO
FO
F0
FO
Fib
. Flb
Fib
Fib '
F2b
P2b
P2b
'»
Fertility
index*
100
86
100
100
100
100
96
100
100
95
100
100
Gestation
index0
100
100
100
100
100
100
100
100
96
95
100
1UO
Vi abi 1 i ty
i ndexc
96
• 95
95
93
88
86
86
89
87
69
81-
85
Lactation
i ndexd
95
86
96
94
92
100
98
99
82
95
99
99
apercantage of females achieving two pregnancies.
bPercentage of pregnancies yielding live births.
cPercentage of rats born that survived for 5 days.
^Percentage of rats alive at 5 days that survived the 21-day lactation period.
SOURCE: Adapted from Paynter et al. (I960).
V-13
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Body weight measurements at weaning and at weekly intervals (for exposed rats
that were allowed to mature) were also comparable to those of controls.
In a teratogenicity study conducted by Hazleton Laboratories Deutschland
(BASF, 1987), groups of inseminated New Zealand White female rabbits (16/group
in the 0-, 30-, and 100-mg dose groups; 19 in the 300-mg dose group) were given
0, 30, 100, or 300 mg/kg/day dalapon (Na/Mg salt, purity 9.9.3%) by oral gavage
on days 6 through 18 of gestation. Three high-dose animals aborted between
days 21 and 25 of gestation. Pregnancy was terminated on day 28 of gestation.
The parameters examined included behavioral change and general observations,
body weight,, and food consumption of each inseminated female rabbit. Upon
sacrifice on day 28, each animal was examined macroscopically for structural or
pathological changes. All fetuses were examined for external malformations.
The pre and postimplantation loss, sex ratio of fetuses, and incidence of fetal
anamolies were comparable between dalapon-treated and control groups. The
results of administration of three doses of dalapon can be summarized as follows:
adminstration of dalapon at 300 mg/kg/day elicited maternal toxicity and
ambryotoxicity. There were significant decreases in maternal body weight gain
and in food and water consumption. Five animals showed an enlarged spleen.
The mean fetal weight was significantly lower than i.n the control group. Admin-
istration of dalapon at 100 mg/kg/day elicited maternal toxicity but did not
elicit emoryotoxicity or teratogenicity. The body weight gain and food consump-
tion were-significantly lower than in the control group. Administration of
dalapon at 30 mg/kg/day did not elicit any adverse effects. Therefore, the
dose of 3U my/kg/day was considered the NOAEL for this study.
In a teratological range-finding test, Thompson et al. (1971) administered
dalapon sodium as an aqueous solution by gavage to pregnant Sprague-Dawley rats
V-14
-------
from days 6 through 15 of gestation. Five treatment groups, each consisting of
6 females, were administered 250, 500, 1,000, 1.5UO, or 2,000 mg/kg/day,
respectively. A control group of six rats received water as the vehicle.
Clinical signs of maternal toxicity consisted of soft stools and slight appetite
depression in the 2,000-mg/kg dosage group. One rat from the 1,500-mg/kg group
had diarrhea. At 1,5UO and 2,000 mg/kg, weight gain of the pregnant dams was
depressed. The fetal resorption rate was increased at both the 1,500- and
2,000-mg/kg dose levels but was not significantly different from that of con-
trols. At 2,000 mg/kg, pup weights were significantly less than those of
controls. No effects were noted at 1,000, 500, or 250 mg/kg/day. Based on
clinical signs of toxicity, a NOAEL of 1,000 mg/kg/day is identified from this
study.
Emerson et al. (1971) reported on the effects of daily administration by
gavage of an aqueous solution of dalapon sodium (500, 1,000, or 1,500 mg/kg/day}
to groups of 25 pregnant Sprague-Oawley rats from days 6-through 15 of gestation.
Animals were sacrificed on day 20 of gestation, and fetuses were removed by
cesarean section. The following parameters were recorded: maternal body
weight on days 0, 6, 15, and 20; number of viable fetuses, resorptions, and
corpora lutea; individual fetal weights and sex; external appearance of pups;
and frequency of skeletal and visceral aonormalities. Mean weight gain.in
dams receiving 500 or 1,500 mg/kg/day and mean daily food consumption in the
1,500- mg/kg/day group were significantly less for the dalapon-treated animals
than for comparable controls over the dosing period (days 6 to 15 of gestation
only). Mean pup weights were significantly less than those of controls in the
1,000- and 1,500-mg/kg/day groups. An increased incidence of delayed ossifi-
cation of sternabrae and the hyoid was observed in the fetuses of dalapon-
treated dams. The authors associated this delayed ossification with the
V-15
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decrease In fetal- weights. Spontaneous major visceral abnormalities consisted
of microphthalmia in one fetus each in the 500- and 1,000-mg/kg/day groups. No
major dose-related skeletal or visceral abnormalities were observed in the
fetuses treated with dalapon sodium and, other than decreased pup weights at
the two higher dose levels, the authors assessed that no adverse effects were
noted. However, delayed ossification is considered developmental toxicity, and
since an increased incidence was noted in fetuses from dams in the 500-, 1,000-,
and l,5UU-mg/kg/day groups compared to controls, a fetal NOAEL was .not obtained
in this study. Based on maternal weight gains, a LOAEL of 500 rag/kg/day is
identified from this study.
In a breeding study with dogs (Dow, 1962a), dalapon was administered to
female beagles at 50 (six dogs), 100 {three dogs), or 200 (one dog) mg/kg
before and'during pregnancy for periods ranging from 2 to 6 months. The dog
given the 2UO-mg/kg dose produced a small, weak litter. No adverse effects on
either reproduction or lactation were noted at the other dose levels in which
12 litters were produced from 10 females. A maternal NOAEL of 100 mg/kg/day
is identified from this study.
0. MUTAGENICITY
Dalapon was not mutagenic in a variety of organisms including Salmonella
typhimurium, Escherichia coli, T4 bacteriophage, Streptomyces coelicolor,
Saccharomyces cerevisiae, and Asperg1l_l_us nidulans (Siebert and Lemperle, 1974;
U.S. EPA, 1984).
Moriya et al. (1983) determined dalapon to be negative in the S^. ty_ph1mu-
rium assay in strains TA98 and TA100, tested according to Ames et al. (1975),
with or without metabolic activation.
V-16
-------
Carere et al. (1978) reported dalapon sodium to be nonmutagenic when
tested for induction of point mutations in four strains of S_. typhimurium
(TA1535, TA1536, TA1537, and TA1538) in the presence or absence of rat liver
microsomal fractions, according to Ames et al. (1973). Dalapon sodium was also
found to be nonmutagenic in a test for the induction of resistance to low
concentrations of streptomycin in the filamentous bacterium^, coelicolor.
Kurinnyi et al. (1982) reported that dalapon, tested at 40, 2UO, or 1,000
mg/kg, increased chromosomal aberrations in mice at the two high doses. The
inadequate technical details presented, however, preclude an evaluation of this
study.
E. CARCINOGENICITY
Paynter et at. (1960) performed a 2-year study in rats fed doses of 0, 5,
15, or 50 mg/kg/day dalapon sodium and a 1-year study in dogs given oral doses
of 0, 15, 50, or 100 mg/kg/day. No tumors were found. However, the details on
the histologically findings from these two studies were not reported, and a
dog study of 1 year's duration was not considered to be of sufficient lengtn to
draw conclusions about the carcinogenic potential of dalapon. Dow Chemical
Company (1983) conducted a 2-year feeding study in which B6C3Fi mice were fed
levels equivalent to 0, 2, 60, or 200 mg/kg/day Dowpon M (see Section V.8). A
"list of selected neoplastic lesions observed in this study is presented in Table
V-6. Male mice receiving 2 and 200 mg/kg/day Dowpon M, had a statistically
significant increase (p <0.05) in the number of animals with two benign hepatic
adenomas when compared to controls. However, there were no increases in the
number of mice with benign liver tumors, malignant liver tumors or total liver
tumors. Therefore, the study authors considered this finding to be coincidental.
The authors also reported a significant trend (p <0.05) towards development of
V-17
-------
Table V-6. Selected Neoplastic Lesions Observed in Mice Fed Dowpon M for 2 Years
Dietary Level {mg/kg/day)
Males
Organ/Lesion
Liver
Adenomas, benign (2)
Adenoma, benign (1)
Carcinoma, malignant
Lymphosarcoma
Pituitary
Adenoma, anterior, benign
•b
Adenoma., alveolar, benign •
Adenocarcinoma, alveolar
malignant
Harderian Gland
Cystadenoma, benign
Mesenteric Lymph Node
Lymphosarcoma
0
(86)
0
10
11
0
(81)
1
(86)
, 7 .
2
(86)
6
5
2
(50)
4*
7
4
0
(45)
0
(50)
IOC
1
(50)
5
3
60
(50)
0
3
3
0
(47)
0
(50)
.IOC-
0
(50)
6
2
200
(50)a
3*
9
9
0
(43)
0
(50)
-..., • 9-.-- :•
0
(50)
11*
5
0
(85)
0
11
0
0
(79)
14
(86)
:8 .
0
(77)
4
13
Females
2
(50)
0
5
1
2
(43)
11
(49)
0
0
(48)
1
10
60
(50)
1
5
2
3
(47)
9
(50)
5
1
(44)
1
2
200
(50)
2
1
0
2
(46)
4
(50)
6
0
(49)
6
11
aNumbers in parentheses represent the
. bThe study authors reported a positive
for males only.
• -Significantly different from controls
: 'Significantly different from controls
number of tissues examined.
linear trend at p <0.05 (Cochran-Armitage Trend
at p <0.05 as calculated by the reviewers.
at p <0.05 as calculated by the study authors.
test)
, SOURCE: Adapted from Dow (1983).
i
•'
.
_•
i •
V-18
-------
i
i
-------
benign lung tumors in male mice. Reevaluation of the data by the reviewers did
not reveal a significant trend using the Cochran-Armitage Trend test, although
significant increases (p <0.05) in the incidence of benign lung tumors at the
low- and mid-dose levels were found. There was a significant increase (p <0.05)
in the incidence of benign cystadenomas of the harderian gland in high-dose
male mice. The incidence was 22% compared to 7% in control males. The study
authors attributed this increase to improved examination methods stating that
the historical incidence had increased after implementation of these new procedures.
Historical control incidences reportedly ranged from 10-18% in males, and 7-9%
in females at 27 months.
F. SUMMARY
' Dalapon has a relatively low order of toxicity to mammals. Acute oral
LDbU values in several species of rodents range from 3,900 to 9,300 mg/kg. A
heifer that received 10 daily doses of 1,000 mg/kg dalapon.showed mild signs
of toxicity but rapidly recovered within 4 days after the last dose. Histo-
logical examination of a calf receiving 1,000 mg/kg/day revealed only a slight
cloudy swelling of the proximal convoluted tubules and hypertrophy or swelling
of tne glome.-ular cells with reduced glomerular space. No toxic effects were
observed in sheep or cattle fed 250 or 500 mg/kg/day for 10 days. In a sub- ^"->*H
chronic study, dogs were dosed initially with 50 mg/kg/day, with the dose then
adjusted upward until the animals were receiving 1,000 mg/kg/day. Vomiting
ensued at tnis hign dose level, and the study was terminated at 81 days.
Except for the vomiting, no other signs of toxicity were evident. Extensive
hematological and biochemical parameters were all normal, as were organ-to-body
weight ratios.
V-19
-------
In rats fed.dalapon in the diet for 97 days at doses of approximately 0,
11.5, 34.6, 115, 346, or 1,150 mg/kg/day, no adverse effects were observed in
male rats at dose levels up to 115 mg/kg/day. In female rats, there were sig-
nificant increases in average kidney weights at 34.6 and 115 mg/kg/day. At the
highest dose levels (346 and 1,150 mg/kg/day), both males and females showed
growth retardation, increased average liver and kidney weights, and slight
histopathological changes in the liver and kidneys. At 346 mg/kg/day, minimal
histopathological changes were seen in the liver and kidneys, while at 34.6 and
115 mg/kg/day, there was an increase in kidney weights of female rats; no micro-
scopic kidney lesions were found. Based on the increased kidney weights, a
NOAEL of 11.5 mg/kg/day is established for rats dosed for the 97-day period.
In a 5-month study, rats administered dalapon sodium in the drinking water
at a level of 200 rag/kg/day showed an increase in weight and histopathological
changes of the thyroid. At the next lower dose level (10 mg/kg/day), rats
>,
showed a decreased -SH level in the serum and a slowing of conditioned reflexes.
No individual data and very few details of the study were presented.
In a 1-year feeding study with mongrel dogs, significant kidney weight
increases occurred in dogs receiving 100 mg/kg/day but not in animals receiving
50 mg/kg/day. Hematological and biochemical parameters, as well as histologi-
cal appearance of tissues, were comparable to controls at all dietary levels.
In a 2-year feeding study in rats, a significant increase in kidney weight was
observed in animals receiving 50 mg/kg/day. At dose levels of 5 or 15 mg/kg/
day, no effects were noted. In this chronic study, 50 my/kg/day can be con-
sidered a LOAEL and 15 my/kg/day a NOAEL. Increased liver weights were noted
»
in mice fed dalapon (Dowpon M) at a level equivalent to 200 mg/kg/day for 2
years.
V-20
-------
Dalapon was nonmutagenic in assays with Salmonella typhimurium strains
TA98, TA100, TA1535, TA1536, TA1537, and TA1538 with or without metabolic
activation; Esch_erj_c_M_a coli, T4 bacteriophage, Saccharomyces c_erevisi_ae.,
Streptomyces coelicolor, and Aspergillus nidulans. One study, for which
technical details were not available, reported an increase in metaphase
chromosomal aberrations in the bone marrow of mice at a dose level of 200 tug/kg
or above.
Tnere were significant increases in incidences of benign lung adenomas in
male mice at 2, 60, and 200 mg/kg/day and benign cystadenomas of the harderian
gland in male mice at 20U mg/kg/day. No tumors were reported in rats fed
dalapon for 2 years. -In-a three-generation study in rats, no effects on
reproductive parameters were found at dose levels up to 3,000 ppm in the diet
(15U mg/kg/day}. In a rabbit teratogenicity study, the only fetal effect noted
was decreased body weights of pups from dams given oral doses of .300 mg/kg/day
dalapon on days 6 though 18 of gestation. No fetal effects were noted at 30 or
1UU mg/kg/day. Similarly, mean pup weights were significantly less than that
of controls when pregnant rats received 1,000 or 1,500 mg/kg/day from days 6
tnrouvjn 15 of gestation but not when fed 500 mg/kg/day over the same period.
No oiner effects on the fetuses were considered to be dose related.
V-21
-------
VI. HEALTH EFFECTS IN HUMANS
A. CLINICAL CASE STUDIES
No clinical case studies reporting the effects of dalapon in humans were
found.
B.. EPIDEMIOLOGICAL STUDIES . .
No epidemiological reports concerning dalapon exposure were found in the
literature.
C. HIGH-RISK POPULATIONS
No data identifying high-risk populations were, found in the literature.
0. SUMMARY
Few data are available on the health effects of dalapon in humans. No
reports of adverse effects in individuals who manufacture or apply dalapon
were found. In an experimental study in humans, only the excretion of the
compound in the urine was discussed.
VI-1
-------
0. SUMMARY
Because of the structural relationship of dalapon (2,2-dichloropropionic
acid) to pyruyic acid and the fact that pyruvate is a major degradative product
of tnis compound in the environment, several investigators have examined the
effects of dalapon on pyruvate-utilizing enzymes in plants and animals.
In rat liver mitochondria, dalapon exerts a weak inhibition of pyruvate
uptake. In plant tissues, dalapon inhibits several enzyme systems that utilize
pyruvate. It was suggested that this innibition may play a role in the toxic
response of plants to dalapon.
VII-2
-------
VII. MECHANISMS OF TOXICITY
A. MECHANISMS IN ANIMALS
Paradies and Papa (1977) measured the effect of several halogenated mono-
carboxylic acids on the rate of uptake of pyruvate into rat liver mitochondria
In vitro. Pyruvate uptake into mitochondria was inhibited only 15% by 2 mM
dalapon, with a Kj of 5.60 mM. This is in contrast to the 42.5% inhibition
caused by 2-chloropropionate, with a KJ of 0.59 mM. These inhibitory effects
were of a purely competitive type. No other information was found on the
mechanism of dalapon action in animal species.
B. MECHANISMS IN PUNTS
Redemann and Meikle (1955) investigated the innibitory role of dalapon on
three enzyme systems involving pyruvic acid: pyruvate oxidase in whole cells
°f Streptococcus faecal is; pyruvate oxidase prepared from•Proteus vulgarls
X-19; and commercially available yeast carboxylase. Pyruvate oxidase from S_.
faecalls was found to be inhibited by dalapon in a complex manner somewhat
resembling noncompetitive inhibition. Yeast carboxylase and pyruvate oxidase
from _P_. vulgaris X-19 both appeared to be competitively as well as noncompeti-
tively inhibited. The authors suggested that dalapon could lead to appreciable
inhibition of pyruvate-utilizing enzyme systems in plants. The role of such a
mecnanism in the overall toxicity of dalapon to plants is unclear.
C. INTERACTIONS
No reports of synergistic or antagonistic effects were found in the
literature.
VII-1
-------
VIII. QUANTIFICATION OF TOXICOLOGICAL EFFECTS
The quantification of toxicological effects of a chemical consists of
separate assessments of noncarcinogenic and carcinogenic 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. .
A. PROCEDURES FOR QUANTIFICATION OF TOXICOLOGICAL EFFECTS
1. Noncarci nogenic Effects
In the quantification of noncarcinogenic effects, a Reference Dose (RfD,
formerly called the Acceptable Daily Intake (ADI)) is calculated. The RfD is '
an estimate (with an uncertainty spanning perhaps an order of magnitude) of a
daily exposure of 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 cnronic study, and divided by an uncertainty factor(s). The RfD is calculated
as follows:
RfD * (NQAEL or LQAEL) = mg/kg bw/day
Uncertainty factorys)
Selection of the uncertainty factor to be employed in the calculation of
the RfD is based on professional judgment while considering the entire data
base of toxicological effects for the chemical. To ensure that uncertainty
factors are selected and applied in a consistent manner, the Office of Drinking
Water (ODW) employs a modification to the guidelines proposed by the National
Academy of Sciences (NAS, 1977, 19BO) as follows:
VIII-1
-------
o An uncertainty factor of 10 is generally used when good chronic or
subchronic human exposure data identifying a NOAEL are available and
are supported by good chronic or subchronic toxicity data in other
species.
o An uncertainty factor of 100 is generally used when good chronic
toxicity data identifying a NOAEL are available for one or more animal
species (and human data are not available), or when good chronic or
subchronic toxicity data identifying a LOAEL in humans are available.
o An uncertainty factor of 1,000 is generally used when limited or
i
incomplete chronic or subchronic toxicity data are available, or when
good chronic or subchronic toxicity data identifying a LOAEL, but.not -
a NOAEL, for one or more animal species are available.
Tne uncertainty factor used for a specific risk assessment is based prin-
cipally on scientific judgment rather than scientific fact and accounts .for ...
possible intra- and interspecies differences. Additional considerations, which
may necessitate the use of an additional uncertainty factor of 1 to 10, not
incorporated in the NAS/ODW guidelines for selection of an uncertainty factor
include the use of a less-than-lifetime study for deriving an RfD, the signifi-
cance of the adverse health effect, pharmacokinetic factors, and the counter-
balancing 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 assumes 100% exposure from drinking water. The DWEL provides the non-
carcinogenic health effects basis for establishing a drinking water standard.
VIII-2
-------
For ingestion data, the DUEL is derived as follows:
DWEL • RfD x (body weight in kg) _ [ mg/L ( ug/i_}
Uriniong water volume in L/day
where:
Body weight = assumed to be 70 kg for an adult. .
Drinking water volume * assumed to be 2 L per day for an adult.
In addition to the RfD and the DWEL, Health Advisories (HAs) for exposures
of shorter duration (One-day, Ten-day, and Longer-term) are determined.
The HA values are used as informal guidance to municipalities and other organi-
zations when emergency spills or contamination situations occur. The HAs are
calculated using an equation similar to the RfD and DWEL; however, the NOAELs
or LOAELs are identified from acute or subchronic studies. The HAs are derived
as follows:
HA = (NOAEL or LQAEL) x (bw) = mqn / ug/Lj
(UFJ x ( L/aayJ
Using the above equation, the following drinking water HAs are developed
for noncarcinogenic effects:
1. One-day HA for a 10-kg child ingesting 1 L water..per day.
2. Ten-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 One-day HA calculated for a 10-kg child assumes a single acute expo-
sure to the chemical and is generally derived from a study of less than 7 days
duration. The Ten-day HA assumes a limited exposure period of 1 to 2 weeks and
VIII-3
-------
is generally derived from a study of less than 30 days duration. The Longer-
term HA is derived for both a 10-kg child and a 70-kg adult and assumes an
exposure period of approximately 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 an animal's lifetime).
2. Carcinogenic Effect^
The EPA categorizes the carcinogenic potential of a chemical, based on
the overall weight of evidence, according to the following scheme:
o Group A: Human Carcinogen. Sufficient evidence exists from epidemiology
studies to support,a causal association between exposure to
the chemical and human cancer.
o Group 8: Probable Human Carcinogen. Sufficient evidence of carcino-
genic! ty in animals with limited (Group Bl) or. inadequate
(Group 82) evidence in humans.
o Group C: Possible Human Carcinogen. Limited evidence of carcinogeni-
city in animals in the absence of human data.
o Group D: Not Classified as to Human Carcinogenicity. Inadequate human
and'animal evidence of carcinogenicity or for which no data
are available.
o Group E: Evidence of Noncarcinogenicity for Humans. No evidence of
carcinogenicity in at least two adequate animal tests in
different species or in both adequate epidemiologic and
animal studies.
VIII-4
-------
If toxicological 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 inges-
tion of the contaminant in drinking water. The data used in these estimates
usually come from lifetime exposure studies in animals. 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 compen-
sates 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 liters of
water per day.
For contaminants with a carcinogenic potential, chemical levels are cor-
related with a carcinogenic risk estimate by employing a cancer potency (unit
risk) value together with the assumption for lifetime-exposure via ingestion of
*
water. The cancer unit risk is usually derived from a linearized multistage
model with a 95% upper confidence limit 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, logit,
and probit. There is little basis in the current understanding of the biologi-
cal mechanisms involved in cancer to suggest that any one of tnese models is
able to predict risk more accurately than any others. Because each model is
based on differing assumptions, the estimates that are 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 due to the systematic and
VIII-5
-------
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 the 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, not for the lower levels of exposure closer to
where a standard may be set. When there is exposure to more than one contami-
nant, additional uncertainty results from a lack of information about possible
synergistic or antagonistic effects.
B. QUANTIFICATION OF NQNCARCINOGENIC EFFECTS FOR DALAPON
1. One-day Health Advisory.
Since no studies found in the literature were suitable for the determina-
tion of a One-day HA value for dalapon, U.S. EPA (1987) recommended that the
Ten-day HA value for a 10-kg child (3.0 mg/L, calculated below) be used as a
conservative estimate of the One-day HA value.
i
2. Ten-day Health Advjsor^ ?
The rat teratology study by Emerson et al. (1971) had been considered to
serve as the basis for determination of the Ten-day HA for a 10-kg child.
However, in this study, tne chemical purity was not specified, and the lowest
dose administered (500 mg/kg/day, LOAEL) had maternal toxicity. A recent
teratology study with rabbits (BASF, 19B7) was selected to serve as the
basis for the'10-day HA. This study specified the purity of the chemical
and provided a lower LUAEL (100 mg/kg/day), and a NOAEL of 30 mg/kg/day.
VIII-6
-------
In this study, groups of inseminated New Zealand white rabbits were given oral
closes of U, 30-, 10U- and 3UU mg/kg/day dalapon (Dowpon M: Na/Mg salt, purity
99.3%) on days 6 through 18 of gestation. Significant decreases in maternal
body weight, in food and water consumption were noted in the mid- and high-
aose groups. Fetal body weight from dames given the high- dose was also -
decreased. However, no adverse effects were noted in the low- dose group,
and a NGAEL of 30 mg/kg/day was identified. Standards for dalapon are
commonly expressed in terms of the acid rather than the salt. Thus, it is
necessary to convert the NOAEL for the Na/Mg salt, 3U mg/kg/day to the
equivalent value for the acid. It is assumed that Oowpon M was
approximately 5:1 mixture of sodium and magnessium salts.
The NOAEL for dalapon as acid = (30 mg/kg/day) (143) (7) = 26.5 mg/kg/day
(165) (5) + (308.6) (1)
where:
30 mg/kg/day = NOAEL for the Na/Ka salt
143 = formula weight of dalapon as acid _ .
165 = molecular weight of sodium dalapon
308.5 * molecular weight of magnesium dalapon
7 = total number of dalapon acid moiety in Dowpon M
5 * number of sodium dalapon in Dowpon M
1 » number of magnesium dalapon in Dowpon M
(each magnesium binds 2 dalapon acid moieties)
Tne Ten-day HA for a lu-kg child is .calculated as follows:
Ten-day HA = (26.5 mg/kg/day)(10 kg) =2.7 mg/L {3,UOO ug/L)
(100)(1 L/day)
where:
26.5 mg/kg/day = NOAEL of dalapon as acid based on body weight
decreases in dams
VIII-7
-------
3.
10 kg = assumed body weight of a child
100 = uncertainty factor, chosen in accordance with
NAS/ODW guidelines for use with a NOAEL from an
animal study
1 L/day - assumed daily water consumption of a child.
Longer-term Health Advisory
Table VIII-2 summarizes the studies considered for the Longer-term HA for
dalapon. The two oral toxicity studies on rats by Kochkin (1967) were not
selected because very few details of the studies were available and the effects
observed could not adequately be assessed. Therefore, the NOAEL and LOAEL could
not be identified. The 80-day oral toxicity study with dogs {Paynter et al.,
1960} was not selected because it was based on only two animals, and increasing
doses were used over an 80-day period.
In a subchronic oral toxicity study by Paynter et al. (1960), a 97-day
exposure of rats to various levels of sodium dalapon (65% pure) in the diet
resulted in an increase in kidney weight of the females at 34.6 mg/kg/day and
higher exposure levels, but not at 11.5 mg/kg/day. A dose-response relation-
snip was observed. A number of hematological, biochemical, and histological
parameters were monitored. From this study, 11.5 mg/kg/day is indicated to be
a NOAEL in rats. Since the increase in kidney weight observed in female rats
receiving 34.6 mg/kg/day or higher doses might be an early sign of an adverse
effect on the kidneys, this dose is taken as the LOAEL. Similarly, in a 2-year
rat chronic dietary study, sodium dalapon exposure (65% pure) resulted in an
increase in male kidney weight at 50-mg/kg/day but not at 15 mg/kg/day (NOAEL).
Considering both Paynter et al. (1960) rat dietary studies together, the highe-r
of NOAEL 15-mg/kg/day for sodium dalapon was chosen to calculate both a
Longer-term HA and a Lifetime HA.
VIII-8
-------
Table VIII-1. Summary of Canidate Studies for Derivation of
the Longer-terra Health Advisory for Dalapon
Reference Species Route
Kochkin Rat Diet
(1967)
Exposure
Duration
2 months
Endpoints
Blood count,
enzyme activ-
NOAEL LOAEL
(mg/kg/day) (mg/kg/day)
<235
(salt)
ity, organ
•weights,
weight gain,
histopathology
Kochkin Rat
(1967)
Paynter et Rat
al. (1960)
Paynter et Rat
al. (1960)
Paynter et Dog
al. (1960)
Oral 5 months
(6 times/
week)
Diet 97 days
Diet 2 years
Oral 80 days
Organ weights,
conditioned
reflexes, vaso-
dilation
Organ and body
weights, histo-
pathology,
growth, food
consumption
Histology,
tissue weights,
body weight
Gross examina-
tion, blood
chemistry,
urinalysis,
organ and
body weights
>1 (salt)
11.5
(salt)
6.5
(acid)
15 (salt)
8 (acid)
__
—
34.6
(salt)
50 (salt)
28 (acid)
__
VIII-9
-------
It is customary to express dalapon standards in terms of the acid rather
than the salt. The NOAEL used to derive the Longer-term HA is based on studies
(Paynter et al., 1960) in which rats were exposed to sodium dalapon that was
65% pure. Thus, a NOAEL for dalapon as the pure acid must be calculated:
The NOAEL for dalapon as pure acid =
(15 mg/kg/day)(0.65)(143) = 8 mg'/kg/day
165
where:
15 mg/kg/day
0.65
143
165
NOAEL for 65% pure sodium dalapon,
purity of sodium dalapoh used in determining NOAEL.
molecular weight of dalapon as acid.
molecular weight of sodium dalapon.
The Longer-term HA for a 10-kg child is calculated as follows:
Longer-term HA = (8 mg/kg/day)(10 kg) =0.3 mg/L .(300 i^g/L) .
(3)(1UO)(1 L/day)
where:
8 my/kg/day * NOAEL, based on kidney weight increases in male rats.
10 kg = assumed body weight of a child.
100 = uncertainty factor, chosen in accordance with NAS/ODW
guidelines for use with a NOAEL from animal study.
1 L/day « assumed daily water consumption of a child.
3 - additional uncertainty factor, chosen to account for the
possible inadequacy of the available animal data.
The Longer-term HA for a 70-kg adult is calculated as follows:
Longer-term HA * (8 mg/kg/day)(70 kg) = 0.9 mg/L (900 ug/L)
- (3)(1UO)U L/day)
VIII-10
-------
where all factors are the same except:
70 kg = assumed body weight of an adult.
2 L/day * assumed daily water consumption of an adult.
4. Reference Dose and Drinking Water Equivalent Level
Table VI11-3 summarizes the studies considered for derivation of the DWEL
for dalapon. The study by Paynter et ai, (1960), involving a 1-year exposure
of dogs to three doses of dalapon in the diet, was not selected because of its
shorter duration. In this study, a NOAEL of 50 mg/kg/day is based on a
statistically significant increase in average kidney weight in dogs receiving
100 mg/kg/day. The study by Kochkin (1967) involving a 5-month exposure of
rats to three doses of dalapon in the diet has not been selected because
very few details of the study (a Russian translation) were available regarding
methods or results, and the importance of the effects observed (decreased
serum sulfhydryl levels and slowed reflexes) could not be adequately assessed.
In a 2-year dietary study in mice by Dow (1983), a slight increase in liver
weights was noted at 200 mg/kg/day. A NOAEL of 60 mg/kg/day was identified.
The study by Paynter et al. (1960), involving a 2-year exposure of rats to
tnree levels of dalapon in the diet, has been selected to serve as the basis for
calculation of the RfD and DWEL because rats appear to be the most sensitive
species to dalapon toxicity. In this "study (Table VIII-3), a slight statistically
significant increase in kidney weights was noted at 50 mg/kg/day. Although no
histopathological findings were observed in the heavy kidneys, changes in organ
weights may be an early indicator of an adverse effect and a conservative
approach was adopted for identifying the NOAEL which was 15 mg/kg/day for this
study.
VIII-11
-------
Table VI11-2. Summary of Candidate Studies for
Derivation of the DWEL for DaUpon
Exposure
Reference Species Route Duration Endpoints
• NOAEL LOAEL
(mg/kg/day) (mg/kg/day)
Paynter
et al.
(196U)
Dow
(1983)
Paynter
et al.
(1960)
Kochkin
(1967)
Dog
Diet 1 year Kidney weight 50 (salt) 100 (salt)
Mice Diet 2 years Liver weight 60 (salt) 200 (salt)
Rat
Rat
Diet
Diet
2 years. Kidney weight 15 (salt) 50 (salt)
8 (acid) 28 (acid)
5 months Decreased
serum
sulfhydryl
levels; slowed
reflexes
>1 (salt)
i
i
VIII-12
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Since the NOAEL used to derive the RfD is based on sodium dalapon that was
65% pure, it is necessary to convert the NOAEL for dalapon as pure acid.
The NOAEL for dalapon as pure acid *
(IS mg/kg/day)(0.65)(143) = 8 mg/kg/day
165
where:
15 mg/kg/day « NOAEL for 65% pure sodium dalapon.
0.65 = purity of sodium dalapon used in determining NOAEL.
143 = molecular weight of dalapon as acid.
165 = molecular weight of sodium dalapon.
The additional uncertainty factor appears warranted because the majority of
studies within the extensive database were conducted prior to 1960 and may be
inadequate according to present standards, although the validity cannot be
assessed using the available data.
The RfD and OWEL for a 7U-kg adult are calculated as follows:
Step 1: Determination of the Reference Dose (RfD)
RfD = (8 mg/kg/day) = 0.027 mg/kg/day
UOOK3)
where:
8 mg/kg/day = NOAEL for 100% dalapon as acid.
100 « uncertainty factor, chosen in accordance with NAS/ODW
guidelines for use with a NOAEL from an animal study.
3 = additional uncertainty factor, chosen to account for the
possible inadequacy of the available animal data.
VIII-13
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Step 2: Determination of the Drinking Water Equivalent Level (DWEL)
DUEL = (0.027 mg/kg/day)(70 kg) • U.9 mg/L (900 ug/L)
( 2 L/day)
where:
0.027 mg/kg/day = RfD.
70 kg - assumed body weight of an adult.
2 L/day = assumed daily water consumption of an adult.
This DWEL calculation assumes that 100% of the human exposure is derived
from drinking water. The DWEL may be modified upon the availability of rela-
tive source contribution data providing estimates of human exposure from food,
air, and possibly the occupational environment. The ultimate goal is to estab-
lish a DWEL so that human exposure from all sources does not exceed the RfD.
C. QUANTIFICATION OF CARCINOGENIC EFFECTS FOR DALAPON
The data on the carcinogenic potential of dalapon are equivocal. No
tumors were reportedly found in Carsworth rats after ingestion of approximately
5, 15 or 50 mg/kg/day for 2 years (Paynter et al., I960), However, in a 2-year
dietary study in B6C3Fi mice reported by Dow {1983}, increased incidences of
benign lung adenomas were obtained in male mice fed 2, 60 or 20U mg/kg/day
(increases were significant at the low- and mid-dose levels). In addition,
significantly increased incidences of benign cystadenomas of the harderian
gland were observed in male mice fed 200 mg/kg/day. No increased incidences
of tumors were noted in female mice. Therefore, this study may provide
limited evidence of carcinogenicity in that dalapon ingestion resulted in
significantly increased incidences of benign lung and harderian gland tumors
in male mice. The lack of historical control data, however, makes it difficult
VIII-14
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to evaluate the toxicological significance of the increased occurance of benign
•harderian gland tumors. This chemical has not been classified for human
carcinogenic potential by the U.S. EPA.
0. EXISTING GUIDELINES AND STANDARDS
The U.S. EPA criterion for the oral exposure of dalapon is based on
noncarcinogenic risk (IRIS, 1988, fron^ Paynter et al.( I960). The American
Conference of Governmental Industrial Hygienists (ACGIH, 1987) recommends a
Time-Weighted Average-Threshold Limit Value (TWA-TLV) of 1 ppm (6 mg/m3).
E. SUMMARY
Table VIII-4 summarizes the HA and DUEL values (calculated on the basis
of noncarcinogenic endpoints). No high-risk populations have been identified,
and no synergistic or antagonistic interactions of dalapon with other chemicals
are recognized. No beneficial effects of dalapon in mammals are recognized.
Dalapon, however, is an effective herbicide with low environmental persistence
and a relatively low order of toxicity.
VIII-15
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Table VIII-3. Summary of Quantification of Toxicological Effects for Dalapon
Value
One-day HA for 10-kg child
Ten-day HA for 10-kg child
Longer-term HA for 10-kg child
Lonyer-term HA for 70-kg adult
DWEL (70-kg adult}
Drinking water
concentration
(ug/L)
a
3,000
300
900
900
Reference
—
BASF (1987)
Paynter et al .
Paynter et al .
Paynter et al .
(I960)
(1960)
(I960)
The Ten-day HA value for a 10-kg child is recommended as a conservative estimate
of the One-day HA value.
VIII-16
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IX-4
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Leasure JK. 1964. Metabolism of herbicides. The halogenated aliphatic acids.
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