Source: Reuters, July 7, 2003

Transcription

1 Ambient Air Quality Gene Schroder, PhD Learning Objectives Identify the components of air pollution and their sources. Review the health effects of exposure to air pollutants. Evaluate the various solutions to air quality control. Statement of Problem Estimated 2-3% of all deaths in U.S. are attributed to air pollution-induced induced respiratory or cardiovascular diseases. World Bank estimates that 2-5% of all deaths in developing countries are due to particulate pollution alone. - Nadakavukaren Statement of Problem Some air pollutants act as asphyxiating agents that deprive the body of oxygen. (CO, HS). Others act as irritants (O 3, SO 2, SO 3, NO 2 ). Chronic exposure to some particulates (coal, asbestos, silicone, cotton, saw dust, metal grindings) cause a variety of distinctive diseases. These are usually occupational exposures.

2 Statement of Problem - Asthma Between 1980 and 1994, the prevalence of asthma increased 75% overall and 74% among children 5 to 14 years of age. Asthma now affects nearly 5 million people who are younger than 18 years of age. Low-income populations, minorities, and children living in inner cities experience disproportionately higher morbidity and mortality due to asthma. Asthma accounts for 14 million lost days of school missed annually. Asthma is the third-ranking ranking cause of hospitalization among those younger than 15 years of age. The number of children dying from asthma increased almost threefold from 93 in 1979 to 266 in The estimated cost of treating asthma in those younger than 18 years of age is $3.2 billion per year. Statement of Problem Fine Particulates A study by Sierra Club of Canda, The Public Health Impact of Diesel Particulate Matter, shows as many as 13,600 Canadians will develop cancer over their lifetimes because of exposure to diesel particulate matter (DPM). The report found exposure to DPM causes an estimated 800 non-cancer premature deaths, tens of thousands of asthma attacks, and hundreds of bronchitis hospital admissions each year in Canada. Diesel bus mechanics, people operating and driving trucks, heavy equipment and tractors, and those in other highly exposed occupations faced an average 33 to 47 percent greater risk of developing lung cancer because of their exposure to DPM at work. Also, children riding on diesel school buses are exposed to levels of DPM that, over a lifetime, would lead to an excess cancer rate of up to one in 256. Source: Reuters, July 7, 2003 Statement of Problem Fine Particulates Study funded by NIEHS (JAMA, March 2002) Assessed the impact of particles smaller than 2.5 microns in cities across the United States. Followed 500,000 adults from 1982 to 1998 as part of an ongoing cancer study. The data, which included cause of death, were linked to air pollution levels for cities nationwide controlled for individual risk factors, such as age, smoking status, body mass, and diet, as well as for regional differences among the study populations. Statement of Problem Fine Particulates Study funded by NIEHS (JAMA, March 2002) " found that the risk of dying from lung cancer as well as heart disease in the most polluted cities was comparable to the risk associated with nonsmokers being exposed to second-hand smoke over a long period of time." Deaths from lung cancer increases by 8% for every 10 micrograms of fine particulate matter per cubic meter, according to the study. Larger particles and gaseous pollutants were generally not as associated with higher number of deaths. Source: Source:

3 Statement of Problem - Ozone State of the Air: American Lung Association Monitored air quality and health in 692 counties around the country (>198 million people). 55.8% of counties received F due to high ozone days. Nearly half of the US population 137,206,767 (49%) lives in areas with unhealthy levels of ozone despite modest improvements in air quality monitored between million fewer live in counties that received an F than last year. Probably improved weather. 1.5 million with emphysema live in F counties. 70% of adults (7.5 million) and children (2 million) with asthma live in F counties. Scope of Problem Outdoor Air Pollution Criteria Air Pollutants Toxic Air Pollutants Acid Rain Indoor Air Pollution Home Sick Building Syndrome Source: Definitions Air pollutants are airborne gases and aerosols that occur in concentrations that threaten the well-being of organisms or disrupt the orderly functioning of the environment. Primary air pollutants pollute the air when emitted. Examples include lead or ozone. Secondary air Pollutants are created by chemical reactions between primary air pollutants in the atmosphere. May involve sunlight or a catalyst. Examples include smog, acid precipitation.

4 Major Air Pollutants Oxides of Carbon: odorless, colorless Carbon dioxide (CO 2 ) fourth most common atmospheric gas produced from oxidation of hydrocarbons asphixiant greenhouse gas Carbon monoxide (CO) toxic in low concentrations produced by incomplete combustion of fossil fuels Major Air Pollutants Volatile Hydrocarbons: (VOC s) Methane, terpenes Mostly natural sources (marshes, ruminants, rice paddies, trees) Benzene, tetrachloroethylene, gasoline, formaldehyde, many others Products of chemical industry used as solvents, paints, cleaning agents, etc. All may form secondary pollutants that irritate eyes and damage respiratory system (photochemical smog).

5 Major Air Pollutants Oxides of Nitrogen Nitric Oxide (NO) Produced by soil microbes Forms NO 2 in combination with oxygen in atmosphere Nitrous Oxide (N 2 O) Natural and man made sources Anesthetic Greenhouse gas Nitrogen Dioxide (NO 2 ) Formed in auto engines and electrical generating plants May contribute to heart, lung, liver and kidney diseases at high concentration Responsible for brownish haze (smog) Forms nitric acid in rainwater (2 o pollutant) Major Air Pollutants Compounds of Sulfur: Sulfur Oxides (SO 2, SO 3, SO 4 ) volcanoes, sea spray, combustion of fossil fuels (coal) irritate respiratory passages (SO 2 ) form acidic aerosols, acid rain (SO 3, SO 4 ) damage lakes, forests, steel and masonry structures. Hydrogen Sulfide produced in anaerobic environment bad odor, toxic asphixiant, explosive Major Air Pollutants Photochemical Smog Mixture of suspended particles and gases formed when oxides of nitrogen and hydrocarbons react in sunlight. PAN (peroxyacetyl nitrates) and ozone are common constituents of smog. At high levels (0.5 ppm), ozone irritates eyes and respiratory passages. Photochemical Smog Forms in bright sunlight from: nitrogen oxides Hydrocarbons (VOCs) oxygen interact chemically to produce powerful oxidants like ozone (O3) and peroxyacetyl nitrate (PAN PAN). These secondary pollutants are damaging to plant life and lead to the formation of photochemical smog. PAN is primarily responsible for the eye irritation so characteristic of this type of smog

6 Photochemical Smog Photochemical Smog Major Air Pollutants Suspended Particulates (aerosols) Includes dust, soot, acid mist, sea spray, trace metals, fungal spores. In urban areas most serious health effects from soot and metal particles, acid mist. Most serious risk from aerosols with cross sectional diameter less than 2.5 microns and sulfate particles. Greatest threat to health among air pollutants (Dockery, 1993) Particulate Matter

7 Air Pollution Legislation First Clean Air Act grants for first air pollution control agencies and first federal regulatory authority abatement conferences Motor Vehicle Air Pollution Control Act authorized federal emission standards for new vehicles amended to include stationary sources gave federal government authority to adopt and enforce regulations in areas with air pollution problems. Air Quality Control Regions (AQCR s) State Implementation Plans amendments required EPA to publish list of pollutants with health or welfare effects. 6 criteria pollutants (NAAQS s) control techniques (BAT) Control pollution at the sources Each state submits an implementation plan description of existing air quality sources of pollutants and emission levels measures taken to achieve standards Transportation Control Plans SIP s not adequate to control auto emissions in some areas. EPA first allowed states to document extent of problem then was forced to require states to submit plans to lower auto pollutants. Implementation included: park and ride facilities surcharge on downtown parking exclusive bus and bicycle lanes state-run inspection and maintenance systems retrofit older cars gas rationing Law gives EPA vast powers Priority or Criteria Air Pollutants Pollutants whose discharge and concentration in the atmosphere are regulated under the Clean Air Act. National Ambient Air Quality Standards (NAAQS) have been established for: carbon monoxide Lead nitrogen dioxide particulate matter (PM 10 and PM 2.5 ) ozone sulfur dioxide States are struggling with Ozone and PM

8 Clean Air Act Amendments Lowered emissions of NO x and VOCs small industrial sources (paint shops, dry cleaners, bakeries) zero emission autos reformulated fuels Reduce SO 2 emissions from coal burning power plants by half by Regulate 188 toxic air pollutants Controversial and expensive Market-based Solutions 1990 Clean Air Act Amendments created a trading system for emission offsets. Regional emission levels are set Companies have limits to pollutants Company may buy an offset from another company in compliance, or implement changes to bring their own operation into compliance. Carbon taxes on fuels burned not politically attractive Amendments to CAA Based on review of scientific evidence of health risks, tighter restrictions placed on ozone and PM 2.5 New ozone standard based on 8 hour average of 0.08 ppm rather than 1 hour average of 0.12 ppm. (1 ppm = 1 µg/m 3 ) New PM 2.5 standard recognizes that these extremely small particles are responsible for both health and visibility problems. EPA estimates that the new standards, along with clean air programs already planned, will reduce premature deaths by about 15,000 a year and serious respiratory problems in children by about 250,000 cases a year. Houston Galveston Area SIP HGA must meet 1 hr ozone standard by November 2007 HGA produced 1,284 tpd of NO 2 in 1993 Must reduce this by 750 tpd Must reduce VOCs by 25%

9 Texas SIP Control Strategies Vehicle Inspection/Maintenance (I/M) see following slide Texas Emissions Reduction Plan (TERP) grants and rebates for low emissions trucks and buses Emissions Bank and Trade Program - trading of NOx allowances Vehicle Idling Restrictions large vehicles allowed to idle no more than 5 minutes Clean Diesel low VOC and sulfur diesel Clean Gasoline low sulfur and low vapor pressure gasoline Gas-fired Water Heaters, Small Boilers, and Process Heaters new units must be low NOx Texas SIP Control Strategies Small, Spark-Ignition Engine Operating Restrictions commercial use of small engines not allowed in morning hours in the summer California Spark-Ignition Engines I can t figure what engines are regulated Voluntary Mobile Emissions Reduction Program (VMEP) variety of voluntary steps to replace polluting vehicles and other sources Transportation Control Measures (TCM) HGA/DFW variety of measures to reduce vehicle miles Speed Limit Reduction - 65 MPH max speed limits in DFW and HGA ) Point source NOx Reductions focuses on point sources Vehicle Maintenance and Inspection Motorists must successfully pass both the emissions and safety portions of the inspection to obtain an inspection sticker. Gasoline vehicles from 2 through 24 years old are tested annually beginning with the vehicle's second anniversary. Remote sensing element to randomly test vehicles on highways. All testing stations are connected to a central database for verification. Recognized emission repair technicians and facilities ensure quality repair of vehicles. Waivers for eligible citizens. 1-Hour Ozone Levels

10 8-Hour Ozone Levels Hazardous or Toxic Air Pollutants Clear evidence for serious health effects No safe exposure levels originally assumed Standards quickly set for asbestos, beryllium, benzene, mercury, vinyl chloride, radionuclides, inorganic arsenic, coke oven 188 substances were listed in the Clean Air Act Amendments of 1990 Risk-based standards now set for 80 categories categories include emissions from big sources (chemical plants, oil refineries, steel mills) and small sources (dry cleaners, electroplating shops (1.5 million ton reduction) Levels of benzene, toluene and other tailpipe emissions regulated (expect 75% reduction by 2020) sources, exposures, health effects are being studied

11 Prevention of Significant Deterioration EPA regulations designed to maintain air quality in areas meeting NAAQS. Test case near Grand Canyon 74 amendments allowed power companies to switch to coal from oil. Allowed more time to comply to sulfur and particulates regulations. Required the same degree of control on all new sources in given category regardless of location. Dispersal of Air Pollutants Boundary layer : near-surface layer of atmosphere that receives pollutants. Boundary layer meteorology determine dispersal of pollutants. Movement of air affected by: topography proximity to water frontal activity climate Temperature Inversion Typical temperature profile shows cooling with altitude. Warm air is less dense than cool air and can hold more moisture. warm air tends to rise above cooler air. As air rises it cools adiabatically (without exchange of energy with surrounding air masses) dry air cooling = 10 o C/km moist air = 6 o C/km looses moisture

12 Temperature Inversion Temperature Inversion Warm air will rise until it reaches common temperature (density). Carries away pollutants Temperature inversion occurs when cooler air is trapped near surface below warmer air mass. Air stagnates and holds pollutants near surface until inversion breaks up. Oceans, mountains, and valleys Temperature Inversion Radiational Temperature Inversion Cold, night air moves down into valley where it is trapped under warmer air mass Temperature Inversion Advection Inversion air descending the leeward slopes is warmed by compression and overlies cold air advected on northerly surface winds (responsible for Denver s air quality problems). Source: Source:

13 Temperature Inversion Subsidence Temperature Inversion Develops aloft as a result of air gradually sinking over a broad area and warmed by adiabatic compression ( high pressure system ) Acid Deposition Combustion gases containing SO 2 and NO 2 carried downwind are converted to strong acids (H 2 SO 4 and HNO 3 secondary air pollutants). Rain, snow and dry particulates deposit acid onto surfaces. ph may be below 4.5 Buffering capacity of soil and watershed determine impact on plants and aquatic life. Acid may have direct effects on plant tissues or mobilize cations in soil to toxic levels. Health effects may be direct (lung tissues) or indirect (heavy metals) Acid Deposition Acid Deposition Source:

14 Acid Deposition Acid Deposition images Acid Deposition Acid Deposition photos/acidrainanalysis.jpg

15 Acid Deposition Acid Deposition Indoor Air Pollution In 1990 EPA ranked indoor air pollution as most important environmental cause of cancers. Sick building syndrome Costs of these health problems tens of billions of dollars. Cigarette smoke and radon lead the list. Building materials Heating and cooking aerosol sprays insecticides dry cleaned clothes

16 Indoor Air Pollution Workplace Air Pollutants