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Section B
What Is Benzene, and Who Is Exposed?
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Tox Paradigm for Benzene
3
Chemical and Physical Properties of Benzene
! Benzene (C6H6) has the following chemical and physical properties:
- Molecular weight: 78.1
- Description: clear, colorless, highly flammable liquid
- Boiling point: 80.1°C
- Melting point: 5.5°C
- Density: d4 0.8787
- Refractive index: nD29 1.5016
- Volatility: vapor pressure of 74.6 mm Hg at 20°C
- Solubility: slightly soluble in water (0.8 part by weight in 1,000
- parts of water at 20°C)
Miscible with acetone, alcohol, carbon disulfide, carbon
tetrachloride, chloroform, ether, glacial acetic acid and oils
4
Sources of Benzene Exposure: Smokers
5
Sources of Benzene Exposure: Nonsmokers
10%
6
These Population Groups May Be Exposed to Benzene
! Workers engaged in its
production
! Workers in chemical industries
using benzene as an
intermediate
! People living in industrialized
towns near factories producing
or employing benzene, or
compounds containing it
! The general overall population
- Benzene is contained in
! ! Workers in industries producing
material containing benzene
Workers utilizing or handling
compounds containing benzene
- A constituent in gasoline
gasoline
- It can be found as a
contaminant in drinking
water
- A solvent in rubber cement
- Impurity in industrial
toluene
7
Recommended Occupational Exposure Limit—Benzene
Year
Guideline
Source
1941
100 ppm (8-hr TWA)
US DOL
1947
50 ppm (8-hr TWA)
ACGIH
1948
35 ppm (8-hr TWA)
ACGIH
1957
25 ppm (8-hr TWA)
ACGIH
1963
25 ppm (ceiling value)
ACGIH
1969
10 ppm (8-hr TWA)
ACGIH
1971
10 ppm (8-hr TWA)
OSHA
1974
25 ppm (ceiling value)
OSHA
1987
1 ppm (8-hr TWA)
OSHA
1989
Proposed 0.1 ppm (8-hr TWA)
ACGIH
1995
Proposed 0.3 ppm (8-hr TWA)
ACGIH
8
Local Air Is a “Soup” of Pollutants
Carbon tetrachloride
9
Benzene Exposures and Theoretical Risk in the US
Activity
Smoking
Intake (µg/day)
Cases/year
1,800
500
50
50
120
150
Driving car
40
40
Filling gas tank
10
5
10,000
10
150
200
Passive smoking
Outdoors
Occupational
Other personal
Drinking water at current MCL
10
0.01
10