Issue 1, Number 3 - Fall/Winter 2011

Upstream health care:
Keeping our air clean

By Barbara Lee

Sonoma County is blessed in so many ways: from beautiful scenery to fabulous local food, great weather to fine wines, and an exciting mix of activities and entertainment. It’s no wonder this is a place people come to embrace a healthy lifestyle. But there’s something more that makes Sonoma County a healthy, beautiful place to live: we have some of the cleanest air in California!

We know how clean our air is because air monitors actually measure the levels of different types of pollution every day. Measured levels are compared regularly with health-based standards set by the state and federal governments. If our air quality doesn’t meet these standards, the sources of the pollution must be identified and programs established to reduce pollution.

Sonoma County spans two air regions. The southern portion of the County, which includes most of Sonoma County’s incorporated cities, is managed by the Bay Area Air Quality Management District, which encompasses eight other counties around the San Francisco Bay. The Northern Sonoma County Air Pollution Control District manages the remainder, which includes Healdsburg, Cloverdale, towns along the lower Russian River, and the entire Sonoma Coast.

Tracking pollutants in our air

Air quality monitoring in Sonoma County focuses on two main types of air pollution: ozone, which is the key part of smog, and small particles. Other pollutants are tracked also.

Ozone is a reactive gas that is not visible to the human eye. High up in the atmosphere it forms an important layer known as stratospheric ozone that protects all living things from ultra-violet radiation. But when formed near the ground, ozone can be harmful to human respiration and damaging to native plants, forests, and agricultural crops. Ground-level ozone forms when vehicle exhaust and other combustion emissions mix with organic vapors such as gasoline, paints, and solvents in the presence of sunlight. Ozone is highest in the summertime when hot weather and still air trap this gas close to the ground.

Ozone’s effects are similar to bleach; in fact, some pool cleaner systems use ozone instead of chlorine to disinfect the water. It has a pungent smell; you may have smelled this in the air after a nearby lightning strike. Breathing ozone can damage the tissues in your airway, causing inflammation; at higher doses, this makes lung cells more permeable and therefore more susceptible to toxins and microorganisms. Key symptoms of ozone exposure include coughing, chest tightness, and worsening of asthma.

The U.S. Environmental Protection Agency has established standards for the amount of ozone that can safely be allowed in ambient air—that is, the air we breathe. The California Air Resources Board has also set standards, which are more protective, but both agencies have based their standards on thousands of studies of the effects of exposure to ozone. Ambient air quality standards have been set and revised for the last 40 years in this manner. There is a current effort in Congress to change the EPA’s methodology for determining what level of pollution is considered safe by including a cost analysis to achieve that level. This would be similar to deciding whether a bacteria strain is harmful based on the cost of treating the infection, or whether a bridge is safe based on the cost of repairing it.

Two air-monitoring stations located in Santa Rosa and Healdsburg measure ambient levels of ozone in Sonoma County. Although the air quality in the Bay Area District as a whole does not meet state and federal standards for ozone, the Santa Rosa monitoring station indicates that the ozone levels in South Sonoma County are below the required safety threshold. In the North County, the air is even cleaner. In fact, in 2010, air in the Northern Sonoma District was found to meet all federal and state standards for all pollutants, making it some of the cleanest air in California.

Air particles: A primer

Particle pollution in Sonoma County comes from a variety of sources including vehicle exhaust, fireplaces and woodstoves, pollens, fertilizers and pesticides, and a small amount of other industrial processes. Particle pollution is highest on cold, windless evenings in the winter months, when smoke from fireplaces lingers near the ground.

Particles have varying chemical make-ups. For air quality monitoring purposes, particles are categorized by size (expressed in terms of microns or “μm”) mostly because this determines how readily they can enter the human body. Generally speaking, larger particles come from the breakdown of crustal materials such as dust from rocks, sand, salts, etc. Smaller particles also come from powdery dusts, chemical dusts (dry fertilizer, for example), and industrial processes, especially combustion. Pollen particles span a wide range of sizes (between 1 μm and 500 μm in size), but the particles that are responsible for most allergy symptoms are between 15 μm and 40 μm.

Particles in a random sample of air could include dust, sand, blowing debris, pollen, smoke, disbursed fertilizer, pesticides—anything that isn’t a gas or water vapor. If you took a handful of dust and tossed it up, the bigger particles would fall to the ground, much as what happens to the dust cloud after a truck rolls over a dirt road. Once the larger particles settle, there is a faint haze left from the particles that remain in the air. These are known as total suspended particles and can be as large as 100 μm in diameter but are usually smaller than 40 μm. These particles are of interest because they are in the human breathing zone, even though most will be filtered out by our natural respiratory defenses (the hairs in our nasal passages and airway) and carried out of our bodies in mucous. Because our natural defenses do a pretty good job protecting us from these larger particles, there aren’t ambient air quality standards for them, but air quality managers do take steps to minimize their presence in the air.

The size of a particle determines how far past our bodies’ defenses it can penetrate. Of most concern are particles small enough to penetrate deep into our lungs, specifically known as inhalable and fine particles. Inhalable particles are generally smaller than 10 microns in diameter (PM₁₀)[1] and come mostly from fine dust and combustion. By comparison, the average human hair is about 70 microns in diameter and fine grains of beach sand are about 90 microns.

Because inhalable particles remain deep in our lungs, they can cause inflammation and other health impacts. Recent research suggests that some of the most severe impacts are the result of smaller particles in this size grouping, referred to as fine particles, and there is now a separate ambient standard for them.

Fine particles are a subset of inhalable particles and are so small—2.5 μm or smaller (PM_2.5)—that they penetrate through tissues and are carried by blood and lymph systems throughout the body where they interfere with cellular processes. Particles of this size tend to have more reactive chemical compositions and are therefore thought to be responsible for most of the health impacts associated with particle air pollution. Fine particles come mostly from combustion associated with factories, cars, fireplaces, and woodstoves.

Inhalable and fine particles have been shown to cause or contribute to a long list of adverse health effects, including: increased respiratory symptoms, pneumonia, bronchitis, and chronic obstructive pulmonary disease; exacerbation of asthma; increased hospital admissions and emergency room visits; increased risk of premature births and infant mortality; and an increase in cancer, cardiovascular, and respiratory deaths, as well as increased total mortality.

Ultrafine particles are even smaller still: less than 0.1 μm, or 100 nanometers in size. Research shows that these particles increase atherosclerotic plaque development and inflammation in heart disease, may heighten allergic inflammation in asthma, and may mediate tumor formation. Because the study of these particles is a relatively new field, much of the research findings are preliminary and suggestive, rather than conclusive and definitive. For this reason, there is not yet an ambient air quality standard for ultrafine particles.

In Sonoma County, inhalable particles are measured at stations in Santa Rosa, Guerneville, Healdsburg, and Cloverdale. Air quality in all four areas consistently meets the federal standards.[2] The Santa Rosa station occasionally shows inhalable particle levels exceeding the California standard.[3]

The fine particle monitor in Santa Rosa indicates that levels meet both federal and state standards,[4] as does the air in northern Sonoma County. The Santa Rosa station also monitors carbon monoxide, oxides of nitrogen, and air toxics. None of these pollutants are detected at levels of concern. A network of three monitors in the mountains above Northern Sonoma also measures hydrogen sulfide, which is released with the steam from the geothermal power operations in the Geysers. These measured levels meet California safety standards.

Air quality affects children the most

Children are especially sensitive to the effects of air pollution because their respiratory systems are still developing and because their higher breathing rate gives them a greater effective dose of air contaminants compared to adults breathing the same air. Children also tend to be more physically active more frequently, which further elevates their breathing rates.

The Children’s Health Study[5] has measured the effects of exposure to high levels of air pollution on children over time in Southern California since 1992. Comparing children in socio-economically matched communities in areas with high levels of pollution to those areas with cleaner air, the study has startling findings. The lungs of children living with higher air pollution grow and develop slower, and they don’t function as well as the lungs of children in cleaner air areas. These children also had a higher incidence of asthma and asthma-related bronchitis, a higher risk of new-onset asthma, and more school days missed. When these children moved to areas with cleaner air, their lungs resumed a more normal growth rate, but they did not recover their lost lung function.

The increased rate of asthma among the general population is a cause of great concern and ongoing study. Asthma is a complex respiratory disease governed by the interaction of multiple genetic and environmental factors. Although air pollution has been shown to play an important role in certain types of asthma, other environmental factors—notably allergens —are key contributors to the disease, especially in Sonoma County.

Protect your respiratory health

Keeping Sonoma County’s air clean is not the sole responsibility of air quality control agencies. Everybody must help. Here are simple steps each of us can take to reduce exposure to outdoor pollutants for better overall respiratory health:

• If you have a choice, live further away from high-traffic roadways.
• Reduce pollution by using your vehicle less.
• Do not run your lawn mower or light your barbeque or fireplace when air quality is forecast to be poor.
• Replace high emitting engines, barbeques, woodstoves, and fireplaces with cleaner, more energy efficient ones (and look for incentives to help!).
• Stand further away from the gas pump nozzle when refueling.
• Use paints and consumer products with very low or no organic vapors (VOCs) and make sure you have good ventilation when using solvents in confined spaces.
• If you suffer from a respiratory illness, pay careful attention to all advisories about air quality and limit strenuous activity when pollution levels are elevated.
• Never use an indoor air purifier that generates ozone.

Most importantly: get outside and enjoy Sonoma County’s clean air!

1. “PM” stands for “Particulate Matter” and the number refers to the size designation – here it is 10 μm.
2. The National Ambient Air Quality Standard for PM10 is 1[5]0 ug/m3 averaged over a 24 hour period.
3. The California Ambient Air Quality Standards for PM10 are 50 ug/m3 averaged over a 24-hour period, and 20 ug/m3 averaged over one year.
4. The National Ambient Air Quality Standards for PM2.5 are 35 ug/m3 averaged over a 24 hour period, and 15 ug/m3 averaged over a year; the California standard is 12 ug/m3 averaged over a year.
5. The Children’s Health Study has been led by scientists at the University of Southern California, and funded by the California Air Resources Board, the South Coast Air Quality Management District, and a grant from the National Institute of Environmental Health. For more information: http://www.arb.ca.gov/research/chs/chs.htm

About the author: Barbara Lee is the Air Pollution Control Officer for the Northern Sonoma County Air Pollution Control Distric.t She has more than 20 years of experience in the field of air quality and chairs statewide and national committees on air quality related issues. She holds a degree in chemical engineering from the Massachusetts Institute of Technology where she also engaged in research in neuroscience.