Ozone (O3, ground-level)

Properties
A colorless gas that is the major constituent of photochemical smog.

Sources
Formed as a result of chemical reactions between oxygen, volatile organic compounds (VOCs), and oxides of nitrogen (NOX). Sources of VOCs and NOX include vehicles, factories, landfills, industrial solvents, and miscellaneous small sources such as gas stations, lawn equipment, etc.

Effects
Irritates the respiratory tract; produces impaired lung function such as inability to take a deep breath; causes throat irritation, chest pain, cough, lung inflammation, and possibly susceptibility to lung infection; aggravates existing respiratory conditions like asthma in certain individuals; may reduce yield of agricultural crops and injure forests and other vegetation.

Description
Complete information on ozone, including levels measured in New Hampshire, is available on the Ozone (Smog) page.

Particle Pollution (Particulate Matter, PM)

Properties
Solid matter or liquid droplets from smoke, dust, fly ash, and condensing vapors. PM is subdivided into particles smaller than 2.5 microns in diameter (PM2.5) and those between 2.5 and 10 microns in diameter (PMcoarse), both of which have specific sources and health concerns.

Sources
Result of burning of wood, diesel and other fuels; industrial plants; agriculture (plowing, burning of fields); unpaved roads and construction.

Effects
Causes nose and throat irritation, lung damage, bronchitis, and possibly premature death. Children, the elderly, and people suffering from heart or lung disease are especially at risk. Also damages paint, soils clothing and furniture, and reduces visibility.

Description
Complete information on particle pollution is available on the Particle Pollution (Particulate Matter) page.

Carbon Monoxide (CO)

Properties
An odorless, colorless gas resulting from incomplete fossil fuel combustion.

Sources
Automobiles, buses, trucks, small engines, boilers and some industrial processes. High concentrations can be found in confined spaces like parking garages, poorly ventilated tunnels, or traffic intersections, especially during peak hours.

Effects
Reduces the ability of blood to deliver oxygen to vital tissues affecting the cardiovascular and nervous systems. Symptoms include dizziness, headaches, nausea, fatigue, memory and visual impairment, and decreased muscular control and ability to exercise.

Description
CO is a colorless, odorless gas resulting from the incomplete combustion of fuels, most typically from cars, trucks, furnaces, and power plants.

Higher levels of CO occur in more urbanized areas, such as Nashua and Manchester, where there are more cars, trucks and other sources and there is a potential for heavy, congested motor vehicle traffic. Areas recording the highest CO levels are ordinarily localized since they are usually associated with roadway intersections. Because carbon monoxide concentrations vary considerably over short distances, areas with relatively higher CO levels are called "hot spots." Hot spot locations include areas with high traffic volumes and congestion, usually caused by traffic signals in an area surrounded or enclosed by buildings. The buildings create a "canyon effect" entrapping carbon monoxide in a confined space. Since carbon monoxide is heavier than air it tends to remain at ground level. The close proximity of buildings does not allow the pollutant to disperse, creating the potential for higher levels of CO in areas occupied by pedestrians and motorists.

There is also a significant seasonal variation in CO emissions and ambient air concentrations with peaks occurring during the winter months because cold engines typically run at a lower air to fuel ratio and the catalytic converter must reach firing temperature before it operates efficiently. In addition, during the winter, concentrations of CO often build up to high levels due to more frequent temperature inversions which trap pollutants.

The Cities of Manchester and Nashua had been designated nonattainment for CO since the 1970s due to violations of the federal CO standard. Levels of CO have improved significantly since the 1980s in Manchester and Nashua due to federal tailpipe standards for new automobiles and traffic flow improvements in the two cities. In addition, there was a required annual emissions inspection program for most motor vehicles from 1986 to 1994 in the Nashua area (Nashua and 11 surrounding communities). As a result of these efforts, New Hampshire has been in attainment of the National Ambient Air Quality Standard for CO since the mid-1990s and CO trends continue to indicate an improvement in air quality.

Nitrogen Dioxide (NO2)

Properties
Causes respiratory illnesses and lung disease and is a significant component of smog.

Sources
A component of NOX (a smog-forming chemical). Results from burning fuels in utilities, industrial boilers, automobiles, and trucks.

Effects
Major pollutant that causes smog, acid rain, and contributes to PM2.5. Can harm humans and vegetation when concentrations are sufficiently high. May cause lung damage and illnesses of breathing passages and lungs.

Description
Nitrogen oxides (NOX) are a blend of multiple air pollutants that result from various combustion processes. The "x"; in NOX stands for one or more oxygen atoms connected to the nitrogen atom. NOX typically occurs as nitrogen oxide (NO) and nitrogen dioxide (NO2), which are very commonly emitted in our everyday lives. Sources include power plants, gasoline and diesel engines (cars, trucks, generators, lawnmowers and yard equipment, snowmobiles, power boats, etc), home furnaces (gas, oil, and wood), industrial processes, explosives, and fertilizers. NOX contributes to several air pollution problems.

One component of NOX that is considered a direct health risk is NO2, which is the actual NOX related pollutant with an assigned National Ambient Air Quality Standard (NAAQS). It can cause respiratory illness and lung damage. High levels can cause edema, and prolonged high exposure can produce fatal lung damage.

NOX is a primary component to ozone (or smog) formation. Ozone forms when NOX and certain volatile organic compounds chemically react in the presence of strong sunlight (ultraviolet wavelengths). An oxygen atom is moved from NO2 to oxygen in the air, creating ozone (O3) – another criteria pollutant. Reducing emissions of NOX is critical to reducing ozone.

NOX is also a major contributor to acid rain (or acid deposition). After NOX is released by a source, it travels and chemically reacts in the atmosphere, eventually becoming ammonium nitrate or nitric acid. Ammonium nitrate is a small particle (PM2.5, which is considered to be another criteria pollutant with its own NAAQS), and it also is a visibility-impairing pollutant. Nitric acid is removed from the air through precipitation (rain, snow, etc.), settling of particles, and by condensation from the air onto surfaces, similar to the formation of dew. Acid deposition damages our forests, lakes, and wetlands by robbing them of necessary nutrients and lowering the pH levels, often to levels below what native species can tolerate. The end result of this process is not a void of wildlife, but rather a shifting of species, where a more tolerant species simply populates an area where native species once were dominant. Nitric acid accounts for about one-third of the acidity in precipitation in New Hampshire.

Another effect of NOX is the nitrification of lakes, ponds, estuaries, and other wetlands. Nitrogen acts as a fertilizer for plants, and when it is added to water, algae and other aquatic plants may multiply excessively, displacing other inhabitants of the wetland.

While NOX emission controls have been added to power plants and automobiles (catalytic converters), growth in energy demand and the amount of vehicle-miles-traveled have offset some of the benefits of the control measures. In New Hampshire, measured NO2 levels have remained relatively stable over the last 20 years, and have shown a slight overall decline. New Hampshire is in attainment of the NO2 NAAQS on a state-wide basis.

Sulfur Dioxide (SO2)

Properties
A colorless gas, odorless at low concentrations but pungent at very high concentrations.

Sources
Emitted from industrial, institutional and utility boilers; petroleum refineries; smelters; paper mills; and chemical plants.

Effects
May cause breathing problems and permanent damage to lungs; contributes to acid rain, which can damage trees, lakes, and corrode surfaces; contributes to the formation of PM2.5, which has negative health effects and reduces visibility.

Description
SO2 is a colorless gas which is best known for being emitted from stationary sources that burn fossil fuels (coal, oil) such as power plants, ore smelters and refineries. SO2 is also released from mobile sources (especially diesel burning vehicles), residential oil furnaces, and large marine vessels. Direct health impact from SO2 pollution is usually near the release point of the source.

With increasing distance from the source, atmospheric chemistry converts SO2 into various related compounds including ammonium sulfate and sulfuric acid. Ammonium sulfate is a small particle (PM2.5, another criteria pollutant with specific health effects), and it is the leading visibility-impairing pollutant throughout the Northeast. Sulfuric acid, originating from SO2, accounts for about two-thirds of the acidity of the acid deposition (rain, snow, fog) in New Hampshire. Acid deposition strips nutrients from soils, weakening vegetation, and it acidifies water bodies, affecting the wildlife that depends on that water. SO2 reductions are considered critical in programs to reduce acid rain and improve visibility.

Following recorded violations of the National Ambient Air Quality Standard in the late 1970s, which were related to the former pulp and paper industry in the Berlin area, sulfur dioxide levels have improved. New Hampshire is currently in attainment for sulfur dioxide and has had no violations of the standard since the early 1980s.

Lead (Pb)

Properties
A heavy metal which can cause adverse health effects either through ingestion or direct inhalation.

Sources
Lead-contaminated soil, dust, and paint; transportation sources using lead in their fuels; coal combustion, smelters, car battery plants, and combustion of garbage containing lead products.

Effects
Elevated levels can cause brain and other nervous system damage and adversely affect kidney function, blood chemistry, and digestion. Children are at special risk. Lead can also harm wildlife.

Description
Lead can be found in the air in gaseous and particle forms depending on the source. Ingested lead can cause liver disease and it interferes with normal nervous system functions and blood formation. It can also interfere with reproduction and cardiovascular systems, and with increased exposure, brain damage and retardation can result. Sources contributing to lead air pollution consist of motor vehicle exhaust, aviation fuels, lead smelters and battery manufacturing plants, and the burning of lead-based paints.

Unhealthful levels of atmospheric lead are very uncommon since the federal requirement of removing lead as a gasoline additive in the early 1980s. Today’s fuels contain only trace amounts of lead, thus significantly reducing airborne lead. All other sources of lead air pollution are only of local significance and are not a measurable problem in New Hampshire.