MIDDLESEX
COUNTY
MIDDLESEX County Average 2005 NATA Modeled Air Concentrations Compared to Health Benchmarks |
Pollutant |
Modeled
Air Concentration (ug/m3) |
Health
Benchmark (ug/m3) |
Risk
Ratio |
%
Contribution from |
Point Sources |
Nonpoint
Sources |
On-road
Mobile Sources |
Nonroad
Mobile Sources |
Background & Secondary |
Acetaldehyde |
2.0 |
0.45 |
4.5 |
<1% |
4% |
7% |
3% |
86%* |
Acrolein |
0.059 |
0.020 |
3 |
<1% |
18% |
17% |
9% |
56%* |
Arsenic Compounds |
0.00072 |
0.00023 |
3.1 |
2% |
6% |
5% |
3% |
84% |
Benzene |
1.4 |
0.13 |
11 |
1% |
13% |
31% |
12% |
43% |
1,3-Butadiene |
0.095 |
0.033 |
2.9 |
<1% |
<1% |
46% |
18% |
36% |
Cadmium Compounds |
0.000097 |
0.00024 |
0.4 |
10% |
37% |
0% |
<1% |
53% |
Carbon Tetrachloride |
0.61 |
0.067 |
9.1 |
0% |
<1% |
0% |
0% |
100% |
Chloroform |
0.13 |
0.043 |
3 |
1% |
52% |
0% |
0% |
47% |
Chromium (hexavalent form) |
0 |
0.000083 |
3.9 |
21% |
7% |
4% |
<1% |
68% |
Cobalt Compounds |
0.000045 |
0.00011 |
0.4 |
87% |
13% |
0% |
0% |
0% |
1,4-Dichlorobenzene |
0.10 |
0.091 |
1.1 |
1% |
54% |
0% |
0% |
45% |
1,3-Dichloropropene |
0.11 |
0.25 |
0.4 |
0% |
100% |
0% |
0% |
0% |
Diesel Particulate Matter |
1.2 |
0.0033 |
381 |
0% |
0% |
57% |
43% |
0% |
Ethylbenzene |
0.39 |
0.4 |
1 |
2% |
34% |
42% |
22% |
0% |
Ethylene Oxide |
0.0096 |
0.011 |
0.9 |
14% |
6% |
0% |
0% |
80% |
Formaldehyde |
2.2 |
0.077 |
29 |
<1% |
3% |
10% |
5% |
82%* |
Methyl Chloride |
1.2 |
0.56 |
2.2 |
<1% |
<1% |
0% |
0% |
100% |
Naphthalene |
0.14 |
0.029 |
4.8 |
3% |
45% |
27% |
3% |
22% |
Nickel Compounds |
0.0013 |
0.0021 |
0.6 |
31% |
25% |
2% |
2% |
40% |
PAH/POM |
0.012 |
0.0072** |
1.7 |
<1% |
81% |
10% |
9% |
0% |
Perchloroethylene |
0.29 |
0.17 |
1.7 |
<1% |
43% |
0% |
0% |
57% |
1,1,2-Trichloroethane |
7.6E-6 |
0.063 |
1.0E-4 |
87% |
13% |
0% |
0% |
0% |
|
Chemicals with risk ratios greater than or equal to 1 are
in bold.
Risk Ratios based on noncarcinogenic effects are in italics.
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. *Acetaldehyde, acrolein and formaldehyde concentration estimates include secondary formation, which is the process by which chemicals in the air are transformed into other chemicals.
**PAH/POM is "polycyclic aromatic hydrocarbons/polycyclic organic matter." These define a broad class of compounds. The chemicals making up this class were broken up into 8 groups based on toxicity, and each group was assigned a cancer-weighted toxicity estimate. 0.0072 ug/m3 is the health benchmark average across the 8 groups. |
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