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.
