Middlesex County Average 2002 NATA Modeled Air Concentrations Compared to Health Benchmarks
Pollutant
Modeled
Air Concentration (ug/m3)
Health
Benchmark (ug/m3)
Risk
Ratio
%
Contribution from
Major Sources
Area
Sources
On-road
Mobile Sources
Nonroad
Mobile Sources
Background
Acetaldehyde
3
0.45
6
0.01%
3%
35%
8%
54%
Acrolein
0.1
0.020
5
0.1%
11%
70%
19%
0%
Arsenic Compounds
0.0007
0.00023
3
2%
6%
6%
4%
82%
Benzene
2
0.13
14
1%
13%
41%
11%
34%
1,3-Butadiene
0.1
0.033
3
0.4%
0.03%
50%
18%
32%
Cadmium Compounds
0.0001
0.00024
0.4
10%
37%
0%
1%
52%
Carbon Tetrachloride
0.6
0.067
9
0.001%
0.2%
0%
0%
99.8%
Chloroform
0.1
0.043
3
1%
52%
0%
0%
47%
Chromium (hexavalent form)
0.0003
0.000083
4
17%
8%
5%
1%
69%
1,4-Dichlorobenzene
0.1
0.091
1.1
0.4%
55%
0%
0%
45%
1,3-Dichloropropene
0.1
0.25
0.4
0.00008%
100%
0%
0%
0%
Diesel Particulate Matter
2
0.0033
498
0%
0%
32%
68%
*
Ethylbenzene
0.5
0.4
1.3
4%
25%
52%
19%
0%
Ethylene Oxide
0.009
0.011
0.8
8%
6%
0%
0%
86%
Formaldehyde
2
0.077
30
0.1%
3%
26%
12%
59%
Methyl Chloride
1
0.56
2
0.04%
0.5%
0%
0%
99.5%
Methyl tert-butyl ether
2
3.8
0.6
2%
13%
41%
44%
0%
Naphthalene
0.1
0.029
4
3%
54%
13%
3%
27%
PAH/POM
0.01
0.0075
1.7
1%
77%
14%
8%
0%
Perchloroethylene
0.3
0.17
1.7
1%
42%
0%
0%
57%
1,1,2-Trichloroethane
2.9E-6
0.063
5.0E-5
66%
34%
0%
0%
0%
Chemicals with risk ratios greater than or equal to 1 are
in bold.
Risk Ratios in italics are based on noncarcinogenic effects.
The symbol ug/m3 is micrograms per cubic meter,
the amount (in micrograms) of a chemical in a cubic
meter of air. This is also known as a concentration.
* For diesel particulate matter, onroad and nonroad
concentrations include a model-estimated background
concentration.
