Air toxics are chemicals released into the air that are known or suspected to cause cancer, or other serious health problems, such as birth defects or reproductive effects. The Federal Clean Air Act, as amended in 1990, lists 188 of these materials, called hazardous air pollutants. California air toxics legislation lists 729 of these substances, referring to them as toxic air contaminants. Some examples of air toxics include: benzene, butadiene, formaldehyde, and hydrogen sulfide.
No. Typically local district monitoring station networks are set up to meet federal and state requirements to monitor levels of six pollutants (called “criteria” pollutants): nitrogen oxides (NOx), sulfur dioxide, particulate matter, carbon monoxide, lead, and ground-level ozone.
There is little hard data available on monitored levels of air toxics. The California Air Resources Board has 21 air toxics monitoring stations around the state, but recently closed the only such station in Santa Barbara County, which was located in downtown Santa Barbara. The United States Environmental Protection Agency (USEPA) has begun a pilot project setting up air toxics monitors and may be more active in this area in coming years.
The data from the now-closed toxics monitoring station show a downward trend in levels of toxics, particularly toxics found in vehicle exhaust. From 1990 to 1996, levels of benzene decreased by 76%, and levels of 1,3-butadiene decreased by 50%. There are also downward trends in levels of perchloroethylene (used in dry cleaning) and hexavalent chromium (an industrial pollutant).
Air toxics are emitted by mobile sources (cars, trucks, trains, and vessels), stationary sources (industrial facilities) and area sources (natural sources, and a variety of products such as paints or household cleaners). In California, emissions from mobile sources are regulated by the USEPA and the state Air Resources Board.
APCD’s air toxics program tracks toxic air emissions from stationary sources. APCD also develops “industry-wide” toxic emission inventories for smaller stationary sources, such as dry cleaners and gasoline stations. The APCD program was set up to implement and enforce the California Air Toxics “Hot Spots” Information and Assessment Act, signed into law in 1987. This Act, also known as AB 2588, requires businesses and industries throughout the state to: –quantify (inventory) and report their emissions of some 729 listed air toxics; –assess the possible health risks from their emissions; –notify members of the public who are exposed to significant risks attributable to their emissions; –take steps to reduce this risk.
When Congress amended the federal Clean Air Act in 1990, it expanded the scope of air toxics regulation by adding provisions to develop control standards for hazardous air pollutants (HAPs). These standards are called Maximum Achievable Control Technology (MACT) standards. States and local agencies such as APCD are responsible for implementing and enforcing the MACT standards, which require the use of control technologies to achieve emission reductions in industries that are major sources of HAPs (such as the aerospace or oil and gas industries), as well as in facilities that make up area sources of HAPs (such as dry cleaners). APCD’s program to enforce the federal provisions, commonly known as Title III, is not as fully developed as its toxics “Hot Spots” program, but will be a focus in the future.
The Air Toxics “Hot Spots” Act requires the California Air Resources Board (ARB) to maintain a list of toxic air pollutants that may cause adverse health affects. The list is contained in Appendices A-I and A-II of the ARB’s Air Toxic “Hot Spots” Emission Inventory Criteria and Guidelines Regulation (CGR). The list, which is updated annually, contains chemicals that have been shown to cause adverse health effects.
A business is subject to the Act if:
- The business manufactures, formulates, uses, or releases any listed substance, or any substance that reacts to form a listed substance; or
- The business is included in a current list of air toxic sources prepared by the APCD.
1. Reporting Businesses that use or emit one or more listed toxic air contaminant must report their emissions of each listed substance. For most small businesses, this is accomplished by completing a questionnaire which includes information on the type and quantity of materials that they use. The APCD then develops industry-wide inventories of air toxics based on the information provided.
When introduced into the program, larger or more complex businesses are required to submit to the APCD a Toxic Emissions Inventory Plan which describes the methods they will use to calculate their toxic air emissions. Once this plan is approved, the businesses prepare and submit a Toxic Emissions Inventory Report which quantifies their actual toxic emissions.
2. Risk Assessment Based on the type and quantity of toxic air pollutants emitted, the APCD ranks each business according to their potential to cause a public health risk. Businesses with a medium or high risk potential are required to complete a health risk assessment. A risk assessment estimates the probability of people contracting cancer or other illnesses from exposure to toxic air contaminants. The APCD has developed a computer model to prepare risk assessments, and will perform this service at no additional cost if requested by the business. With the APCD performing this task, business costs are greatly reduced.
3. Public Notification If results of the risk assessment show that a business poses a significant public health risk, then the business must notify residents in the surrounding area of this risk. Businesses will be required to notify people in writing, and may be required to hold a public meeting to educate the community. APCD staff will also be available to answer questions.
4. Risk Reduction In addition to public notification, a business found to pose a significant public health risk will be required to take steps to reduce that risk within 5 years. To attain this goal, the business must perform an audit to identify changes in operations that will reduce toxic emissions and the associated risk. The business must submit for APCD review a Risk Reduction Plan that includes measures which will be implemented to reduce the health risk from their facility emissions.
5. Updates Small businesses that are part of an industry-wide inventory, such as gas stations, dry cleaners and auto body shops, complete a questionnaire every year as part of the annual report required by their permit.
Businesses that prepare a Toxic Emissions Inventory Plan and Report submit updated information every four years. The update requirements depend upon the risk attributable to the business and the business operations. Businesses that pose a significant health risk must submit an updated Plan and Report every four years. Lower risk facilities must only complete an update summary form. Based upon review of this form, the APCD will notify those facilities that are expected to have a considerable change in their toxics emission inventory of the need to submit an updated plan and report.
Risk refers to the increased potential for negative health effects posed by exposure of individuals to toxic emissions. The risk posed by a particular toxic air contaminant can be a cancer risk or a non-cancer risk, or both. Non-cancer risk can be acute, meaning effects can be felt in a relatively short time after exposure to the substance, or chronic, meaning effects are cumulative from exposure over an extended period of time. Risk assessments are done to estimate the increased risk posed by toxic emissions. Toxic substances can enter the body through multiple pathways, including inhalation (breathing), dermal contact (touching), and ingestion (eating and drinking). The health risk assessment is crafted to account for these pathways.
For facilities that emit significant amounts of air toxics, something known as a risk “isopleth” or “footprint” is developed. This is a map that shows the area of elevated risk around the facility. It is developed taking into account prevailing winds and weather conditions in the area. In some cases the risk footprint may be so small that no one is actually living in the affected area.
Risk assessment results for cancer-causing air toxics are given in terms of the probability that an individual will contract cancer (usually expressed as so many chances in a million). For non-cancer risk, a “Hazard Index” is used. A Hazard Index presents the ratio of the predicted exposure level of a toxic pollutant to the level of exposure considered acceptable by health professionals. If the Hazard Index is more than 1.0, it is considered a significant risk facility (see below). Typically for non-cancer risk the “endpoint” is also identified. This is the part of the body most affected by the particular pollutant.
Background risk is the risk level found throughout an area. This risk is not caused by a particular facility, and may be partly due to air pollution from vehicle traffic. The estimated background cancer risks due to air pollution for some selected areas of Santa Barbara County are as follows:
For cancer risk, if a facility’s toxic air emissions result in a cancer risk of equal to or greater than 10 in a million, it is considered a significant risk facility. For non-cancer risk, if a facility’s toxic air emissions result in a Hazard Index equal to or greater than 1.0, it is considered a significant risk facility. Significant risk facilities are required to reduce their risk, and to notify people living in the risk footprint about the elevated risk.
There are currently no significant risk facilities in Santa Barbara County.