EPA-650/2-75-003
JANUARY 1975
Environmental Protection Technology Series
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EPA-650/2-75-003
SEMINAR SUMMARY:
SAMPLING AND ANALYSIS
OF THE VARIOUS FORMS
OF ATMOSPHERIC LEAD
by
Carole R. Sawicki
Chemistry and Physics Laboratory
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
January 1975
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EPA REVIEW NOTICE
This report has been reviewed by the National Environmental Research
Center - Research Triangle Park, Office of Research and Development,
EPA, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S . Environ-
mental Protection Agency, have been grouped into series. These broad
categories were established to facilitate further development and applica-
tion of environmental technology. Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields. Thefe series are:
1. ENVIRONMENTAL HEALTH'fiFFECTS RESEARCH
2. ENVIRONMENTAL PROTECTIGN~TECHNOLOGY
3. ECOLOGICAL RESEARCH
4. ENVIRONMENTAL MONITORING
5. SOCIOECONOMIC ENVIRONMENTAL STUDIES
6. SCIENTIFIC AND TECHNICAL ASSESSMENT REPORTS
9. MISCELLANEOUS
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
point sources of pollution. This work provides the new or improved
technology required fcr the control and treatment of pollution sources
to meet environmental quality standards.
This document is ava: .able to the public for sale through the National
Technical Information Service, Springfield, Virginia 22161.
11
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CONTENTS
Page
INTRODUCTION 1
PRESENTATIONS 3
JAMES W. ROBINSON LOUISIANA STATE UNIVERSITY 3
R.K. SKOGERBOE COLORADO STATE UNIVERSITY 3
REED ROBERTSON AND JAMES HICKEY NALCO
CHEMICAL COMPANY 5
GARY TER HAAR AND MANUEL BRANDT -- ETHYL CORPORATION ... 6
RALPH PAROD ENVIRONMENTAL HEALTH LABORATORIES, INC. ... 8
E.S. JACOBS DuPONT COMPANY 9
CLAIR C- PATTERSON -- CALIFORNIA INSTITUTE OF TECHNOLOGY. . 10
DISCUSSION 11
CONCLUSIONS 12
111
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ERRATA
FOR
SEMINAR SUMMARY: SAMPLING AND ANALYSIS OF THE VARIOUS
FORMS OF ATMOSPHERIC LEAD
EPA-650/2-75-003
Replace p. iii with the following corrected Table of Contents.
CONTENTS
Page
INTRODUCTION 1
PRESENTATIONS 3
JAMES W. ROBINSON LOUISIANA STATE UNIVERSITY 3
R.K. SKOGERBOE COLORADO STATE UNIVERSITY 4
REED ROBERTSON AND JAMES HICKEY NALCO
CHEMICAL COMPANY 6
GARY TER HAAR AND MANUEL BRANDT ETHYL CORPORATION . . 7
RALPH PAROD ENVIRONMENTAL HEALTH LABORATORIES, INC. . . 9
E.S. JACOBS DuPONT COMPANY 10
CLAIR C. PATTERSON CALIFORNIA INSTITUTE OF TECHNOLOGY. . 11
BENJAMIN Y.H. LIU ~ UNIVERSITY OF MINNESOTA 12
DISCUSSION 13
CONCLUSIONS 14
TECHNICAL REPORT DATA SHEET 15
111
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SEMINAR SUMMARY:
SAMPLING AND ANALYSIS OF THE VARIOUS FORMS
OF ATMOSPHERIC LEAD
INTRODUCTION
Scientists at the Environmental Protection Agency's National
Environmental Research Center, located in the Research Triangle Park,
N.C. , have long been interested in the analysis of atmospheric pollutants.
Of special interest are those hazardous substances found in fairly high
concentrations in blood samples obtained from high-risk groups in various
parts of the country. One such pollutantwell known for its toxicityis
lead, which was the subject of an informal, day-long seminar at the EPA
facility on September 16, 1974.
The objectives of this seminar were twofold: (1) to provide a
useful and timely review of current methods for sampling and analyzing
atmospheric lead; and (2) to consider the latest research data by Drs.
Robinson and Skogerboe which suggest that large quantities of lead pass
through the filters presently being used to measure lead in the air.
The seminar, entitled Sampling and Analysis of the Various Forms
of Atmospheric Lead, included oral presentations by ten prominent
scientists knowledgeable in the problem area. A question-and-answer
session was held after each presentation. This report is a summary of
those informal presentations. The names of the participants and their
affiliations are listed below.
1. James W. Robinson, Professor of Chemistry, Louisiana State Univer-
sity, Baton Rouge, Louisiana.
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2. R.K. Skogerboe, Professor of Chemistry and Atmospheric Science,
Colorado State University, Fort Collins, Colorado.
3. Rred Robertson, Senior Group Leader of the Environmental Services
Laboratory, Nalco Chemical Co. , Chicago, Illinois.
4. James Hickey, Director of Analytical Services Dept. , Nalco Chemical
Co. , Chicago, Illinois.
5. Gary Ter Haar, Senior Research Associate, Petroleum Chemicals
Research, Ethyl Corp. , Detroit, Michigan.
6. Manuel Brandt, Superintendent of Chemical Analysis , Petroleum
Chemicals Research, Ethyl Corp., Detroit, Michigan.
7. Ralph Parod, Ph.D. candidate in Physiology at Wayne State University,
(Represented Environmental Health Laboratories, Inc. , Farmington,
Michigan.)
8. E.S. Jacobs, Superintendent of Automotive Emissions Division ,
DuPont Petroleum Laboratory, Deepwater, New Jersey.
9. Clair C. Patterson, Senior Research Associate., Geochemistry
Division of Geological and Planetary Sciencies, California Institute
of Technology, Pasadena, California.
10. Benjamin Y.H. Liu, Professor and Director, Particle Technology
Laboratory, Mechanical Engineering Dept. , University of Minnesota,
Minneapolis, Minnesota.
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PRESENTATIONS
James W. Robinson Louisiana State University
The instrument used for the determination of particulate and molecular
atmospheric lead was described by Dr. Robinson as being a flameless atomic
absorption device equipped with a 10-mm Micropore carbon disc (0.01-ym pore
size) on the inlet port to filter the particulates, followed by an atomizer
carbon bed to adsorb the molecular species. Dr. Robinson discussed data
on particulate and molecular lead collected on 5 separate days with this
instrument. Feasibility studies were carried out on 2 days to see if there
was a detectable correlation between atmospheric molecular lead concentra-
tion and automobile traffic density. The next 3 days were "all-day" runs
to ascertain any diurnal pattern of lead concentration fluctuation.
The results of the experiments described above showed that near a
parking lot a large proportion of the lead was molecular (in the vapor
phase, as opposed to extremely small particles) . In addition,
Dr. Robinson presented slides which showed that the diurnal maxima for
molecular lead corresponded to peak traffic periods, and that during
windless, high-humidity conditions, the molecular lead built up to very
high concentrations (>50 yg/m^) . Dr. Robinson's explanation for this
phenomenon was that lead from the exhaust deposits on the road and is
then volatized under appropriate conditions of sunlight and humidity.
The speaker indicated that the data obtained on lead by the collection
of particulates from the air with the use of high-volume samplers present
only a partial atmospheric profile because the concentration of the molecu-
lar species of the metal is ignored. Further, the speaker pointed out that
he has also found "molecular" compounds of cadmium, arsenic, zinc, and
selenium using the collection system described, and that these molecular
pollutants might also exist in concentrations significantly higher than are
currently known. Dr. Robinson concluded that much more work needs
to be done before recommendations are made.
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I^.K^ Skogerboe Colorado State University
Dr. Skogerboe described a number of experiments to determine
filter collection efficiencies for several elements, including lead. Initial
field experiments set up at various distances from a busy street in Fort
Collins, Colorado, used sampling trains consisting of a millipore filter
(0.45-pm pore size) and two nitric acid scrubbers connected in series.
The sampling trains were operated simultaneously and continuously for
an average of 8 hours/day at a constant flow rate of 1 liter/minute,
which corresponds to a total air volume of 0.48 m'. Atomic absorption
spectroscopy using the carbon rod was the method used for sample
analysis. Results indicated that, based on finding lead in the nitric
acid scrubbers, lead collection efficiencies on the filter decreased at
greater distances from the street. Intrigued by studies of Spurny et al. ,
who showed that membrane filters tend to pass some of the aerosols in
the 0.1- to 0.4-ym range, Dr. Skogerboe made some lead measurements
and systematically varied the face velocity. The results indicated drop-
off in collection efficiency with increasing face velocity.
Then the speaker described the use of a condensation nucleii
counter to check filter efficiencies. No particles were detected coming
through the filters. New sampling trains were set up consisting of a
millipore filter (0.45-ym pore size) backed by a graphite filter and a
nitric acid scrubber and using the same rate and time as mentioned pre-
viously. From 2 to 30 percent of the total lead was found in the charcoal
traps, and greater percentages were found in the scrubbers (6 to 53 per-
cent) , depending on the distance from the street. Dr. Skogerboe concluded
from these results that the lead reaching the scrubbers must be organic
(gaseous) , which is either not trapped by activated charcoal or, if it is trapped,
gets"oluted" from the charcoal by the air stream. He also presented data
indicating that iron and cadmium get through the filters.
Dr. Skogerboe also discussed work that was done prior to the
field sampling experiments to determine the extent of the lead blank in
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the millipore and graphite filters and in the nitric acid. These values
were as follows:
Millipore filter 0.082 + 0.010 yg Pb/filter
Graphite filter <0.001 yg Pb/filter
Acid scrubber [HNO3/H2O (1:1 v/v)] 0.00042 ug Pb/ml
Comparing these levels to the data collected in the field experiments
showed that concentrations well in excess of the blank levels were
collected.
Dr. Skogerboe presented four graphs depicting the correlations
between membrane filter efficiencies and filter loading for Pb , Fe,
and Cd collected at a constant flow rate. The results showed that as
the filter load increased, the collection efficiency increased, possibly
due to the decrease in pore size of the filter because of loading.
Dr. Skogerboe concluded with the statement that he plans to
conduct further studies intended to give more definitive explanations
for what he has observed.
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Reed Robertson and James Hick^y Nalco Chemical Company
The sampling train described by Mr. Robertson consisted of a
glass fiber or membrane filter, an activated carbon scrubber, and two
impingers in series containing either nitric acid in both or nitric acid
in the first and iodine monochloride in the second. This system was
used to collect a minimum of 15 to 20 cubic meters of air in 24 hours.
High-purity nitrogen and pre-filtered laboratory air were used to
determine average blank values. Lead was added to the activated
carbon in both laboratory and field tests, and recovery studies were
performed. A known amount of organic lead vapor was generated, and
this was collected by the sampling train. Following analysis of the sam-
ples, recovery percentages were calculated. Efficiencies of the nitric
acid scrubber and iodine monochloride scrubber for organic lead were
evaluated by using the sampling train with the activated carbon scrubber
removed.
Based on the results of the studies outlined, the speakers drew
the following conclusions. Lead found in blanks (equivalent to 0.06
yg/m ) is insignificant with large samples (20 m^) of air. Glass
fiber filters pass less than 2 percent of the total lead catch, and
millipore filters pass less than 1 percent. No lead was found on the acti-
vated carbon trap or in the nitric acid or iodine monochloride impingers;
but if any were found, it would be less than the amount in the blanks.
The ASTM procedure for treating activated charcoal recovers lead added
to carbon, 98 to 102 percent by material balance. An iodine monochloride
scrubber is much more efficient for collecting lead than is a nitric acid
scrubber. The use of glass fiber filters in conjunction with high
volumes of sample represents the most efficient sampling technique
availaMe at the present state-of-the-art, according to Mr. Robertson.
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Gary Ter Haar and Manuel Brandt Ethyl Corporation
Mr. Ter Haar described a filtration system for atmospheric lead
which consisted of a glass fiber or membrane filter followed by activated
carbon and a pair of scrubbers, one containing 3N nitric acid and the
other empty. Samples were taken in parallel at 0.75 and 15 liters/minute
for 24 hours at three locations. In another filtration study (flow rate
0.75 liter/minute) membrane and glass fiber filters were followed by
activated carbon and a liquid nitrogen trap. In another study the effi-
ciency of Mine Safety Appliance (MSA) activated carbon (Stock No. 24207)
for tetraethyl lead (TEL) or tetramethyl lead (TML) was tested.
Lead in each sample was determined by atomic absorption after
complexation with sodium diethyldithiocarbamate and extraction into
methyl isobutylketone. At least one blank of each sample type was run
with each group of analyses. Average blank values were used to
correct gross results.
The speaker concluded from the data collected in the studies that
both types of filters demonstrate high efficiency for the collection of
particulate lead and that only a low percentage of organic lead
exists, especially where lead concentrations are somewhat elevated
or when the higher sampling rate is used. At the lower sampling rate,
it was found that the backgrounds on carbon and acid were too large
a part of the total lead found to give dependable results. The blank
values were reported as follows:
Glass fiber or membrane filter 0.9 yg Pb/filter
Carbon 2.0 \ig Pb/2 g sample size
Acid scrubber (3N HNOs) 0.2 yg Pb/ml
These blank values include the filter and carbon or acid plus the chemicals
needed to bring these samples to the point of analysis. When a sample
of 3N nitric acid was analyzed directly by a flameless atomic absorption
technique, the total acid blank was 0.001 to 0.008 yg Pb/ml. However,
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even at the lower sampling rate where blanks values became significant,
average filter efficiencies were high, and organic lead was low. Although
Mr. Ter Haar mentioned that the blanks were higher than he would have
liked, he stressed the importance of sufficient sample size to make
the blanks a small part of the total sample.
In the cryogenic study, Mr. Ter Haar reported that lead which passed
through the filter averaged only 2 percent of the total lead collected.
It was also mentioned that activated carbon quantitatively retained both
tetramethyl and tetraethyle&d, as shown by the MSA study.
The speaker closed with the statement that both glass fiber and
membrane filters are highly efficient in collecting particulate lead in
air and that the small amount of organic lead present is efficiently
collected on activated carbon. The studies of Drs. Robinson and
Skogerboe indicate that measurements of lead as reported by the National
Air Sampling Network are low because of lead passing through the filter;
according to Mr. Ter Haar, this is not so.
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Ralph Parod Environmental Health Laboratories, Inc.
Mr. Parod discussed filter efficiency for lead particulate. The
sampling train used to collect freeway samples consisted of a 0.45-vm
millipore filter followed by two nitric acid scrubbers in series. The
flow rate varied from 4.6 to 10.4 liters/minute. Mr. Parod also reported
results obtained using a closed system for the generation and collection
of lead particulate. The particulate was generated by burning an alco-
holic solution of organic lead (TEL) . The collection system consisted of
a glass fiber or millipore filter (0.45 ym) , an activated charcoal trap,
and two nitric acid scrubbers in series. The flow rate varied from 7 to
9 liters/minute.
The concentration of lead in each sample was determined by the
colorimetric dithizone procedure.
The data acquired from sampling near a freeway showed filter
efficiency for particulate lead to be on the order of 97 percent, whereas
the studies on the closed system, in which lead particulate was generated
and collected, showed efficiencies for glass fiber and millipore filters
approaching 99 percent. Blank values reported were as follows:
Millipore filter 0.025 yg Pb/filter
Glass fiber filter 0.5 yg Pb/filter
Activated charcoal 0.5 yg Pb/g
Acid scrubber (10% HNO3) 0.0006 yg Pb/ml
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E. S^. Jacobs DuPont Company
Dr. Jacobs described the sampling train used for collection of
atmospheric lead as consisting of a millipore filter followed by either
an activated charcoal scrubber or one containing iodine monochloride.
Lead was extracted from the filter and scrubbers and analyzed by atomic
absorption spectroscopy. Results of field studies at five sampling
sites were presented. Also described were studies to determine the
amount of non-filter able lead in vehicle exhaust in 1963 to 1970 auto-
mobiles and experiments designed to determine the mass balance of
lead burned in various engines .
The speaker concluded from his data that only 1 to 3 percent of
total lead in the air and less than 0.1 percent of exhaust lead may pass
through a filter. The particulate lead concentration in car exhaust was
shown to be 100 to 1,000 times greater than that of the organic lead. The
lead balance study on cars which ran for 50,000 or more miles accounted
for better that 95 percent of all the lead used during this mileage accumu-
lation .
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Glair C_. Patterson California Institute of Technology
Dr. Patterson did not deliver a prepared talk, but instead commented
on the material that had been presented. He observed that the researchers
with low blanks found lead that passed through the filter, while those
with high blanks did not. He emphasized the importance of low blank
values for measurement methods of the type discussed.
As an explanation for the high freeway levels of lead found by
some researchers, the speaker also commented on the possibility of large.
amounts of lead-containing particulate depositing on the r< ad and being
volatized under appropriate meteorological conditions.
Dr. Patterson also discussed a cooperative experiment with
Dr. Robinson whereby he would visit the Baton Rouge Laboratory and
collect samples for analysis as Dr. Robinson is monitoring. Dr. Patterson
would return to his laboratory and assay those sa'mples that were
collected at the same time that Dr. Robinson was monitoring a high
"molecular lead" value by an isotope dilution mass spectrometric
technique. This experiment would ascertain the accuracy of
Dr. Robinson's total lead measurement.
LI
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Benjamin Y^ H. Liu University of Minnesota
Dr. Liu discussed the subjects of size distribution of particles
and filter efficiencies. He presented a slide containing a plot of parti-
cle volume versus particle diameter for fresh auto exhaust that showed
a peak between 0.01 and 0.1 ym. He mentioned that the percentage of
particle volume associated with submicron particles varies from 9 percent
in Fort Collins, Colorado, to 69 percent in Los Angeles, California.
On filter efficiency, Dr. Liu reported that when using a 10-ym pore
size Mitex Teflon filter, the minimum efficiency for collection of
0.05-ym particles was found to be 65 percent at 1 cm mercury pressure
drop. For a 5-ym pore size of the same filter and using the same
particle diameter, the minimum collection efficiency was reported to
be 80 percent at 1 cm mercury pressure drop. For both pore sizes of
filters, as the pressure drop was increased, the particle size for minimum
collection efficiency shifted to smaller sizes. In addition, when using
8-ym pore size Nucleopore filters, the efficiency for collection of 0.02
to 0.1-ym particles was found to be 0 percent at 1 cm mercury pressure
drop, increasing to 20 percent at 25 cm mercury pressure drop.
Further, Dr. Liu reported that preliminary measurements on 0.8-ym
millipore filters show that the collection efficiency is essentially 100 per-
cent. He also mentioned that he would like to get some of Dr. Robinson's
Micropore carbon discs and examine them for collection efficiency.
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DISCUSSION
As mentioned previously, this seminar had a double purpose:
1. To review current methods for sampling and analyzing atmospheric
lead.
2. To consider the latest research data by Drs. Robinson and Skogerboe
suggesting that large quantities of lead pass through the filters being
used to measure lead in air.
This lead is termed "organic (gaseous)" by Dr. Skogerboe and "molecular"
by Dr. Robinson.
With regard to the second objective, Dr. Jacobs and Messrs. Parod,
Ter Haar, and Robertson presented data indicating that greater than 95
percent of the total lead is collected on the primary filter and that the small
percentage of organic lead that exists is efficiently collected on the second-
ary carbon filter.
In attempting to compare the results presented, one finds a number
of problem areas. The type of filter for collecting samples varied (mil-
lipore, glass fiber, membrane) as did the blank value of the different
filters. Various types of carbon backup filters were used. The nitric
acid in the scrubbers ranged from doubly redistilled to reagent grade,
and the concentration also varied from investigator to investigator.
Flow rates and sampling times varied from 100 ml/minute for 5 minutes to
15 liters/minute for 24 hours. Further, samples were analyzed colorimetrically
as well as by four different techniques of atomic absorption spectroscopy.
According to Dr. Robinson, humidity had an effect on the amount of
"molecular" lead observed, but no other investigator recorded its value.
Dr. Liu indicated that the concentration of submicron-size particles can
vary from 9 to 69 percent depending on the part of the country in which
samples are collected. The statements by Drs. Robinson and Liu suggest
locational effects on results.
Therefore, any attempt to compare these results for atmospheric
lead is most difficult, because the researchers used different filter
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media, sampling rates, sampling times, reagent purities, and analytical
methods. In addition, sampling locations were diifcrcji.it.
CONCLUSIONS
The conclusions that can be drawn from this seminar are very
clear. There is wide variability in the sampling and analytical
parameters for the analysis cf atmospheric lead. More work must un-
done to determine the effects related to filter media, sampling velocity,
sample handling, and humidity. In addition, substantiation by an in-
dependent investigator and unequivocal characterization of the structure(s)
of "molecular lead" (Robinson) and the nature of the "gaseous lead1'
(Skogerboe) are vitally needed. Only through more research and vital
confirmation studies will we be able to determine the true atmospheric
profile of lead.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-650/275-003
3. RECIPIENT'S ACCESSION*NO.
4. TITLE AND SUBTITLE
SEMINAR SUMMARY: Sampling and Analysis
of the Various Forms of Atmospheric Lead
5. REPORT DATE
January 1975
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Carole R. Sawicki
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
National Environmental Research Center
Chemistry and Physics Laboratory
Research Triangle Park, N.C. 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
National Environmental Research Center
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The sampling and analysis of hazardous substances in the atmosphere are
topics that currently generate substantial interest. One such hazardous sub-
stance, lead, was the subject of a day-long seminar wherein 10 prominent
scientists knowledgeable in the areas of sampling and analysis of the various
forms of atmospheric lead gave oral presentations. The seminar provided
an opportunity to review the current methods for sampling and analyzing at-
mospheric lead and to consider recent research data by two seminar par-
ticipants which suggest that certain forms of atmospheric lead pass through
filters presently being used for measurement. The importance of this obser-
vation stems from the belief that if such lead exists it is likely to be much
more physiologically active than particulate lead. This report summarizes
those various presentations.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS,OPEN ENDED TERMS
c. COSATl l-icld/Group
Lead
Sampling
Analyzing
Atmospheric
13. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (This Report)
none
21. NO. OF PAGES
18
20. SECURITY CLASS (Thispage)
none
22. PRICE
EPA Form 2220-1 (9-73)
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