Effects on Health

In the upper atmosphere, ozone occurs naturally and protects us from the sun’s ultraviolet radiation. At ground level, ozone results from pollution and can harm our health. Ground-level ozone is the primary ingredient of smog in our cities.

Ground-level ozone is formed when other pollutants (nitrogen oxides and volatile organic compound gases) react with sunlight. Sources for these pollutants include motor vehicles, power plants, factories, chemical solvents, combustion products from various fuels, and consumer products.

Ozone can cause numerous health effects. It interferes with lung function and can cause pain and discomfort at concentrations as low at 0.08 ppm (parts per million). Health effects of ozone include:

• chest pain
• coughing
• wheezing
• pulmonary and nasal congestion
• labored breathing
• increased airway permeability and airway inflammation
• faster breathing rates in athletes (the faster the breathing rate, the greater the amount of ozone that can penetrate the respiratory tract)

Ozone exposure can also reduce resistance to infections. Research has shown that immune system cells move into the lungs after acute exposure to ozone, producing a nine-fold increase in disease fighting cells. In addition, short-term ozone exposure has also been shown to decrease resistance to bacterial pneumonia in animal studies.

In Southern California, the effects of ozone can be complicated by the presence of other pollutants, such as nitric acid, particulate matter and nitrogen dioxide. In coastal areas, it is common for the population to be exposed to acidic fog in the morning followed by exposure to high concentrations of ozone during sunny afternoons. Research has shown that ozone mixed with acids can be more harmful than ozone alone.

Scientific studies indicate that the following groups are at particular risk from ozone air pollution.

• Children at play outdoors. They represent the largest group at high risk from air pollution. Children may be at greater risk because, for their body size, they inhale several times more air than adults. They also spend relatively more time outdoors playing hard and breathing heavily through their mouths. As a result, pollution is more likely to come into direct contact with their respiratory systems.
• People with existing lung disease. This includes chronic bronchitis, emphysema and asthma. Since they already suffer from reduced ability to breathe, these individuals are often greatly affected by the increased impairment that can result from exposure to ozone. This group can include many older adults.
• Healthy adults that exert themselves outdoors. This can include farmworkers and construction and road maintenance crews. Even relatively low amounts of ozone can impair the ability of healthy people to breathe during moderate exercise. Ozone levels are generally highest during summer months, when people tend to spend the most time outdoors.
• Athletes exercising outdoors. In studies on people who exercise, normal lung function declined by 10% or more in 20% of the subjects when exposed to ozone. Lung function was further reduced as the ozone level increased. When exposure included exercising at competitive levels, lung function decreased by as much as 30% and chest tightness appeared.

Ground-level ozone can have several environmental impacts: Ozone impairs the ability of plants to produce and store food. This inhibits plant growth and reproduction and diminishes its health, which in turn, weakens its ability to survive disease, insect attacks and extreme weather.

Ozone can reduce agricultural yields and damage economically important crops — including soybeans, kidney beans, wheat and cotton. In Ventura County, there are some crops that can no longer be grown due to ozone air pollution.

Ozone can have long-term impacts on forests and ecosystems including disruption of ecological functions, such as water movement and mineral nutrient cycling, and adverse impacts on the natural habitat of plants and animals.

Particulate matter is a combination of fine solids such as dirt, soil dust, pollens, molds, ashes and soot, and aerosols that are formed in the atmosphere from gaseous combustion. Individually, these particles and droplets are invisible to the naked eye. Collectively, however, they can appear as clouds or a fog-like haze.

Particulate matter less than 2.5 microns in diameter is referred to as fine particles or PM 2.5. In comparison, a human hair is about 70 microns in diameter. Fine particles result from many different sources including wildfire smoke, industrial operations, residential combustion and vehicle exhaust so their composition varies widely. Fine particles also can be formed when combustion gases are chemically transformed into particles.

Particulate matter larger than 2.5 microns in diameter is called coarse particles or PM 10. Coarse particles have many sources, including windblown dust, vehicles traveling on unpaved roads, materials handling, and crushing and grinding operations.

Both coarse and fine particles are health concerns because they can penetrate into the sensitive regions of the respiratory tract. Fine particles are of greatest concern because they are linked to the most serious effects. They can be deeply inhaled into the lungs where they can be absorbed into the bloodstream or remain embedded for long periods of time. They can cause persistent coughs, phlegm, wheezing, and physical discomfort.

Negative effects include premature death, hospital admissions from respiratory causes and increased respiratory symptoms. According to the Environmental Protection Agency (EPA), short-term exposure to course particulate matter can lead to coughing, minor throat irritation and a reduction in lung function. Long-term exposure to particulate matter may increase the rate of respiratory and cardiovascular illness and reduce life span. A portion of urban non-smoker lung cancer risk is due to coarse particulate matter in soot from diesel trucks, buses and cars.

Research has shown that the following groups are especially vulnerable to particulate matter air pollution:

• Children
• Older adults
• People with asthma, chronic bronchitis, emphysema and heart disease

Fine particles can soil human-made materials, speed their deterioration and impair visibility.