What are Toxic Air Pollutants?                              
Toxic or hazardous air pollutants (HAPs) are those pollutants known or suspected to cause cancer or other serious health effects, such as reproductive disorders or birth defects.  The US EPA has defined 188 chemicals as HAPs.  Some are immediately dangerous to human health even in small quantities, whereas some HAPs cause health problems if exposure extends over a longer period of time.  The degree to which a toxic air pollutant affects a person’s health depends on many factors, including the quantity of pollutant the person is exposed to, the duration and frequency of exposures, the toxicity of the chemical, and the person’s state of health and susceptibility.

Where do HAPs come from?

Scientists estimate that millions of tons of HAPs are released into the air each year.  Some are from natural sources such as volcanic eruptions and forest fires.  However, most sources of HAP emissions originate from human activity.  These sources are categorized as: on-road mobile sources which, consist of cars, trucks, and buses; nonroad mobile sources which include small engines, construction equipment, aircraft, marine vessels, and locomotives; point sources which consist of industrial plants, factories and large commercial businesses; and nonpoint or area sources which include the aggregation of numerous small businesses and the emissions from household consumer products.

What are we doing to reduce HAP emissions?

Since the Clean Air Act Amendments of 1990 (CAAA), the EPA has significantly increased emphasis on reducing HAP emissions by promulgating National Emission Standards for Hazardous Air Pollutants (NESHAP) for specific industries.  Most NESHAP regulations apply only to large sources emitting more than 10 tons per year (tpy) of an individual HAP or 25 tpy of all HAPs combined.  However, there are NESHAP regulations currently for 15 area source categories, such as dry cleaners using perchloroethylene that emit <10 tpy of an individual HAP.  Other small sources located in Hillsborough County that are subject to air toxic regulations include aluminum smelters and chrome platters.

In addition, the EPC encourages facilities to eliminate sources of HAP emissions through pollution prevention  (P2) and the air permitting  process.  Sources can reduce air toxic pollution by selecting raw materials that don’t contain HAPs or accepting air permit limitations on HAP emissions.

For more information about HAPs and federal regulations for toxic air pollutants, visit EPA’s Air Toxics web site, and an overview of the Urban Air Toxics Strategy.

What are the levels of HAP emissions in Hillsborough County?

The most recent inventory of hazardous air pollutants for all source categories in Hillsborough County are for the 2002 calendar year.  The inventory was compiled as part of the US EPA’s National Emissions Inventory (NEI).  The process of developing a national inventory takes three years in part because it is compiled from data provided by state and local air quality agencies.

The total emissions of hazardous air pollutants in 2002 were approximately 14,521 tons.  The largest contributions to the total, 38.4% are from cars and trucks.  Industrial sources contribute 32.4% and small businesses and consumer uses add 14.4%.  The remaining emissions are from construction equipment, aircraft, locomotives, and other small engines like lawn and garden equipment that contribute 14.7%.

The largest amount of hazardous air pollutant emitted is hydrochloric acid (HCl) which, primarily comes from the electric power generating plants and municipal waste combustors.  Air toxic emissions of toluene, xylenes, and benzene, each greater than 1000 tons, come mostly from automobiles, trucks and other engines and equipment.

The following table represents 99% of the HAP emissions in Hillsborough County.  The remaining 1% is toxic air pollutants whose individual annual emissions were less than 10 tons.

Which HAPs emitted in Hillsborough County pose the highest risk for cancer?

Toxic air pollutants have varying levels of carcinogenic effects from inhalation over a lifetime of exposure.  A small dose of a highly toxic carcinogen like arsenic may be a greater cancer causing risk to the public than larger amounts of less carcinogenic compounds like chloroform.  The air toxic pollutants emitted in 2002 were ranked according to a toxicity-weighted score based on EPA unit risk factors for inhalation of cancer causing compounds.  As a result, the emissions of nickel compounds pose the highest lifetime cancer risk through inhalation in Hillsborough County.  These pollutants are primarily emitted by electric power generating facilities.

 The following table shows the top ten cancer risk drivers for Hillsborough County.  This data is based on a lifetime exposure to breathing ambient air concentrations due to the level of HAP emissions in calendar year 2002.

2002 Toxicity-weighted Air Pollutants

What other state or federal programs are related to HAP emissions?

Section 112(r) of the Clean Air Act authorizes EPA to establish a program to prevent and prepare for the accidental release of hazardous substances.  The EPA promulgated the Risk Management Rule in July, 1996 that requires facilities handling hazardous materials to develop a risk management plan to prepare for worst-case accidents that may result from natural or man-made disasters.  The plan evaluates the extent of the population impacted by a release and identifies response actions that warn the public, notify local authorities, and mitigate the impacts.  In the State of Florida, this program is regulated by the Florida Department of Community Affairs (DCA), State Emergency Response Commission. The development of a risk management plan is a requirement in the air permit of any facility to which the regulation applies.  Additional information on this program can be obtained from EPA’s Chemical Emergency Preparedness and Prevention Office.