The USEPA has compiled a National-scale Air Toxics Assessment (NATA) for 1999 that
examines exposure to over 100 hazardous air pollutants throughout the country.
The assessment followed the four step process listed below. For more detailed information, go to the National
Air Toxics Assessment (NATA)
1. EMISSION INVENTORY PREPARATION
The emission inventory describes the type and amount
of emissions of HAPs from a wide variety
of sources. USEPA divides the sources into four categories:
- Major (large manufacturing facilities, utilities, etc.)
- Area/nonpoint (small industrial facilities, dry cleaners, residential
fuel combustion, consumer product use, etc.)
- On-road mobile (cars, trucks and buses) and
- Nonroad mobile (construction equipment, agricultural
To see summaries of the NJ emissions information used by
NATA click here.
2. PREDICTING AIR CONCENTRATIONS
The USEPA used a sophisticated dispersion model, known
as ASPEN, to predict how the pollutants from the sources
in the emission inventory would move through the air and
be distributed throughout the country. The results are
shown on the NATA
3. CALCULATING EXPOSURE
USEPA also took the extra step of trying to adjust the
predicted air concentrations to account for activity patterns
that move people around during the day, thus making their
exposure a composite of multiple concentrations experienced
in various places.
4. RISK CHARACTERIZATION
In this step, USEPA considers the risk of both cancer
and non-cancer effects from inhalation of these hazardous air pollutants nationwide. In this analysis they were able to identify
the pollutants posing the most cancer risk nationwide.
They also identified one non-carcinogen (acrolein) as
posing the greatest relative hazard for health effects
other than cancer.
Although the results are not refined enough to suggest
specific risk-based regulatory action, the USEPA expects
that the assessment results can help to:
- Identify air toxics of greatest potential concern.
- Characterize the relative contributions to air toxics
concentrations and population exposures of different
types of air toxics emissions sources (e.g. major, mobile).
- Set priorities for the collection of additional air
toxics data and research to improve estimates of air
toxics concentrations and their potential public health
impacts. Important additional data collection activities
will include upgraded emission inventory information,
ambient toxics monitoring, and information on adverse
effects to health and the environment.
- Track trends over time
in modeled ambient concentrations of toxics.
- Measure progress toward
meeting goals for risk reduction from inhalation of ambient
back to top