Transcript Slide 1

Retrospective Exposure
Assessment for Benzene in the
Australian Petroleum Industry
Glass, D.C.; Adams, G.G.; Manuell, R.W and Bisby,
J.A. (2000) Annual of Occupational Hygiene, Vol.
44(4), pp.301-320
Presented by Charles Christen, DrPH, Med,
Dec. 2010
Exposure Assessment Course (EOH 2504)
Disclaimer
The information supplied in this power
point is taken verbatim from the
literature, the reason for this is to provide
as accurate an account of the study as
possible.
The discussion section is the presenters
own words.
BACKGROUND – BENZENE1
A colorless liquid with a sweet odor.
 Evaporates into air very quickly and
dissolves slightly in water.
 Highly flammable.
 Also known as Benzol
 Benzene has been found in at least 1,000
of the 1,684 current or former National
Priority List (NPL) sites.
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1ATSDR, (2007) Toxic
Substances Portal - Benzene, August,
http://www.atsdr.cdc.gov/PHS/PHS.asp?id=37&tid=14#bookmark01
Industrial Sources and Uses of
Benzene (source:ATSDR)
Made mostly from
petroleum.
 Ranks in the top 20 in
production volume for
chemicals produced in the
U.S..
 Various industries use
benzene to make other
chemicals such as:
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◦ Styrene (for Styrofoam® and
other plastics)
◦ Cumene (for various resins)
◦ Cyclohexane (for nylon and
synthetic fibers).
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Used in the manufacturing
of some types of:
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Rubbers,
Lubricants
Dyes
Detergents
Drugs,
Pesticides.
Also present in:
◦ Crude Oil
◦ Gasoline
◦ Cigarette Smoke
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Natural Sources include:
◦ gas emissions from
volcanoes and forest fires
Exposure to Benzene (source: ATSDR)
Exposure of the general population to benzene
mainly occurs through breathing air that contains
benzene.
 The major sources of benzene exposure:
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Tobacco smoke
Automobile service stations
Exhaust from motor vehicles
Industrial emissions.
Vapors (or gases) from products that contain
benzene, such as:
◦ Glues, Paints, Furniture Wax, and Detergents
Approximately 1/2 of the exposure to benzene in the
United States results from tobacco smoke.
 Auto exhaust and industrial emissions account for
about 20% of the total national exposure to benzene.
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Exposure to Benzene (con’t)
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Measured levels of benzene in outdoor air
have ranged from 0.02 to 34 parts of
benzene per billion parts of air (ppb)
◦ 1 ppb is 1,000 times less than 1 ppm.
People living in cities or industrial areas are
generally exposed to higher levels of
benzene in air than those living in rural
areas.
 Individuals employed in industries that make
or use benzene may be exposed to the
highest levels of benzene.
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Exposure to Benzene (con’t)
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For most people, the level of exposure to
benzene through food, beverages, or drinking
water is not as high as through air.
Exposure can result from breathing in
benzene while showering, bathing, or
cooking with contaminated water.
Benzene may find its way into ground and
surface water through leaks and spills from
underground gasoline storage tanks or from
landfills and hazardous waste sites
Health Effects of Benzene Exposure
(source ATSDR)
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The major factors related to health risk
from exposure to a toxic substance include:
◦ Amount a person is exposed
◦ Length of time of the exposure.
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Brief exposure (5–10 minutes) to very high
levels of benzene in air (10,000–20,000 ppm)
can result in death.
Lower levels (700–3,000 ppm) can cause
drowsiness, dizziness, rapid heart rate,
headaches, tremors, confusion, and
unconsciousness.
Health Effects of Benzene Exposure
(Con’t)
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Breathing benzene for long periods may lead
to harmful effects in the tissues that form
blood cells, especially the bone marrow.
Exposure to benzene may be harmful to the
reproductive organs
The Department of Health and Human
Services has determined that benzene is a
known carcinogen
Both the International Agency for Cancer
Research and the EPA have determined that
benzene is carcinogenic to humans.
Study Background2
Study initiated from results reported from
the Health Watch Epidemiological Health
Surveillance program.
 Health Watch is an epidemiological health
surveillance program conducted by the
University of Melbourne on behalf of the
Australian Institute of Petroleum (AIP)
since 1980.
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2The
following material is taken from the study found in the title for
this presentation.
Study Background (con’t)
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Prospective cohort study of:
◦ All-cause mortality and cancer incidence
◦ 1988 nested case-control study of lymphohaematopoietic (LH) cancers and benzene.
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Participation in the cohort is voluntary and
consists of all employees
◦ Except head office staff and those employed at
sites with fewer than 10 employees.
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Approximately 95% of eligible employees in
the industry have participated in surveys.
An employee is taken into the cohort after
working 5 years in the industry and remains
for life.
Study Background (con’t)
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Early evidence from the cohort surveys
showed that there was an excess of
lympho-haematopoietic (LH) cancers in
workers in the Australian Petroleum
Industry that was twice that expected in
the Australian male population and was
statistically significant.
Study Background (con’t)
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Numerous industry studies have shown
benzene exposure to be associated with
leukemia and multiple myelomas.
◦ (N=14, between 1964-1996)
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The risk of leukemia after exposure to low
concentrations of benzene has been debated
over the past 20 years.
◦ (N=13, between 1977-1966)
Study Background (con’t)
In 1993 early reports of the nested casecontrol study showed a dose-response
relationship based on a qualitative
exposure ranking system for benzene
 By 1996 there were 65 LH cancer cases
each matched to five controls on year of
birth
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Purpose of the Study
To use quantitative exposure assessments
of exposure to benzene for each
individual subject in the nested casecontrol study because a more
sophisticated exposure assessment of
cases and controls was needed.
Method
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Nine year retrospective study
◦ 1981-1983 & 1986-1987 & 1991-1993 & 1994
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N = 390
The authors stated that the methodology
developed and used closely followed other
petroleum industry studies in the USA,
Canada and the UK.
Five occupational hygienists from the largest
petroleum companies collaborated and
reviewed the exposure assessment process.
Method (con’t)
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Job histories complied from the subjects
(case and control) through interviews
conducted in person or by phone.
◦ Company
◦ Site worked per week
◦ Area of work for each calendar period in years
and months
◦ Names and identification of cases and controls
were not included in the data.
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Information provided by the subjects was
cross-checked with company records and
rechecked by the individual.
Method (con’t)
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Site Information (N=209)
◦ Each site were subjects worked or had been located was
contacted and asked to provide a brief site assessment
form
◦ A follow up was performed by one of the five occupational
hygienists.
◦ Questionnaire to gather information on:
 History of the site
 Major changes in staffing, plant, product and technology
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Job Specific Questionnaires
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Tasks
Technology
Products for relevant job activities
Spills, Skin Contact, Cleaning Regimes
Other sources of exposure
Exposure Assessment Model
Major exposure modifying factors (Kfactors) were identified for each specific task
 Measured benzene exposure data was
available for some current tasks and most
jobs but not for all sites.
 Time periods were identified for all
job/activity/site along with specific tasks
 No measured data available the benzene
exposure was estimated using an alogrithm
developed from two previous studies.
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Exposure Assessment Model
Formulas
Task estimates (TE) of exposure for
individual tasks
(TEijk) = BE x Ki x….Kx
BE = Base Estimate, i
= task, j = activity of job k (in ppm), K = factors
adjusting BE, i = 1
Estimated average (AE) benzene
concentration (in ppm) for a subject
during a particular activity.
(AEjk) = S of njk TEijk x (Tijk/Aik)
Tijk=average time in hours/week on task i
Aik = average time in hour/week on jk
Exposure Assessment Model
Formulas
Workplace estimate (WE) of exposure for the
job k (in ppm) and nk is the number of
activities for each job k.
(WEijk) = S of nk (j=1) AEijk x (Ajk/35hour week)
Cumulative Estimate (CE) is the exposure
associated with each of the job titles held by
the subject as recorded in the job history
CE = S of n (k=1) WEk x (Yk)
Yk = number of years spent in job k
N = total number of jobs for the subject
Estimated Average of Exposure = CE/Ytotal
Base Estimates (BE)
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Data for BE were obtained primarily from the participating
petroleum companies in Australia.
When there was no Australian measurable data it was taken
from the literature (primarily CONCAWE3)
A small amount of historic monitoring data from the Risk
Management Division of the New South Wales WorkCover
Authority
Refinery and Terminal background values were taken from
exposure measured on employees carrying out jobs
considered by the petroleum industry occupational health to
have been non-exposed.
Exposure monitoring data from the New South Wales
Commonwealth Scientific and Industrial Research
Organization (CSIRO) and Victorian Environmental
Protection Authorities (VEPA) were used for the urban and
rural background values
3The
oil companies European association for environment, health and safety in refining
and distribution
Criteria for BE
Only person exposure data was used which had not been
normalized to an 8 hour average and included the title of the
work monitored, job site/location and duration of monitoring
 Incomplete data used only when no other data was available
 Data was unacceptable if there was inadequate information
on the monitoring method.
 Information always accompanying data:
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◦ Limit of detection (dl), the technology in use, the products being
handled.
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Samples of less than 180 min duration were excluded.
Data collected over less than 12 min and below dl were
excluded.
A value of .5 dl was used where results were below the dl
Arithmetic means of the data were used for the BE
Skin exposure rating was not developed because little
benzene is absorbed through the skin.
Results
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The CE’s ranged from 0.005 to 50.9 ppmyears (m =5.0 ppm-years, sd =7.0 ppm-years).
Estimates of average benzene concentration
ranged from 0.001 to 1.7 ppm (m =0.24 ppm, sd
=0.28 ppm).
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The estimates of average benzene
concentration was <1 ppm for 97% and <
0.5 ppm for 84% of study subjects.
Overall exposures to benzene in the
Australian petroleum industry were low.
(all activities and jobs < time weighted average of 5 ppm.)
Limitations
Much of the data was taken from the literature,
and individual exposure data, especially for long
term exposure, was lacking.
 The authors state that “the information most
usually omitted from the data were circumstantial
details around the monitoring. “
 Accidental and leak exposure was not taken into
account.
 The values ascribed to some exposure modifiers
were subjective and since BE’s and exposure
modifiers form the basis of the exposure
estimation algorithm the resulting estimates are
uncertain.
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Limitations
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The authors also state “the exposure
estimates in the Australian petroleum
industry have often been made for
compliance purposes or to check “worst
case” scenarios rather than having been
based on sampling strategies and methods
designed to yield data for use in
epidemiology programes.”
Discussion
A glaring issue compromising the exposure
data is that the companies provided the
benzene monitoring data rather than
independent occupational hygienists.
 The monitoring procedures were not
described in the article.
 The data used from the literature is most
frequently data provided by industry for
industry.
 Smoking and truck traffic are major sources
of benzene, it was unclear how this data was
taken into account in the study.
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Discussion
This is a retrospective study with many
gaps in data and estimations.
 Retrospective studies typically involve
recall bias, and missing data.
 Retrospective studies for exposure
assessment are usually not reliable and
used most infrequently.
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