What is NATA?
The National-Scale Air Toxics Assessment (NATA) is a screening assessment that estimates inhalation health risk for cancer and non-cancer health effects. NATA evaluates risk for the 50 states, the District of Columbia, Puerto Rico and the Virgin Islands.

What is risk?
Risk is defined as the probability and degree of harm arising from a given situation or activity. Risks surround us in our everyday lives and influence decisions we make. For more information please see An Introduction to Risk Assessment, Risk Management, and the DAQ Air Toxics Program.

What data are used to estimate risk?
Data are obtained from the National Emission Inventory (NEI), mobile source emission estimates, Residual Risk Technology, the NC Urban Air Toxics (UAT) monitoring network and other ambient air monitoring sources. Population data are taken from the most recent US Census.

How are the results estimated?
Cancer risk is based on the following assumptions: a person is exposed for 24 hours per day, for a 70 year lifetime while living and working in the same geographic area and maintaining the same activity pattern.

How I can interpret NATA results?
NATA estimates are based on computer modeling. For cancer, estimates indicate the additional number of people who may develop cancer given a lifetime exposure to a toxic air pollutant. Other factors, such as genetics and lifestyle, are not considered in these estimates. The results are presented in the number of cases per million population.

Estimates for non-cancer health effects are determined by summing effects of exposure to the same group of organs. The non-cancer results are reported as a "hazard index" where a value of less than one represents a low probability of causing adverse health effects.

What limitations do the NATA results have?
NATA provides a snapshot of how airborne concentrations of air toxics, exposure and risk vary throughout the United States. The study does not focus on individuals, or on the variation in exposure and risk among individuals. It focuses on variation between well-defined geographic areas, such as counties or states.

Comparison of results between NATA study years is not recommended because computer model methodologies used and source data are not the same from year to year.

Results presented in this webpage come from EPA National Air Toxics Assessment (NATA), which contains information related to 1999, 2002 and 2005 NATA.

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