Second in a Three-Part Series
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By William C. Shelton

Somerville has the most excess deaths from lung cancer and heart attacks per square mile of all Massachusetts’ cities and towns. Two thousand scientific studies have identified the killer. Traffic on Routes 93, 28, 38, and 99 produces as much as 1.6 million fine and ultrafine particles in every cubic inch of air. Ultrafines are two ten-millionths of an inch thick, or smaller.

Beyond 500 feet of the traffic, ultrafine particles either evaporate or grow into fine particles, up to one ten-thousandth of an inch in diameter. Both fine and ultrafine particles easily penetrate homes. When inhaled, most are retained deep in the lungs or passed through into the bloodstream.

The Environmental Protection Agency has, in the past, focused on these particles’ affect over a broad region, for example the area within I-495. Over such an area, they produce 6% more heart deaths, and 8% more lung deaths than where people breathe clean air

In recent years, however, accumulating scientific evidence has shown that particles’ effects are much more local and much more deadly than previously thought. Neighborhoods with dirtier air have 25% to 60% more heart and lung disease deaths. Most important for Somerville, people living within 100 meters (325 feet) of a major highway have a 95% higher death rate from lung cancer, heart attacks and other cardiopulmonary diseases than the average population.[i]

How Fine Particles Kill

As epidemiologists have proven that vehicular pollution kills, other scientists have begun to study “how.” Fine particles’ role in promoting lung cancer is not so different from that of cigarette smoke. They interfere with genetic instructions telling cells how to divide and grow.

They also produce a defensive response that damages the lungs. The average person breathes over 5,000 gallons of air per day. The air tubes in the lung, bronchia, end in air sacs, alveoli. There, oxygen, along with ozone, carbon monoxide, etc., passes into the bloodstream.

Most large particles that we inhale are caught by mucous membranes in the nose, throat, trachea, and bronchia, then swallowed and passed out of the body. Bacteria, viruses, and particles smaller than one ten-thousandth of an inch thick go into the air sacs, where there are no mucous membranes.

Large white blood cells surround them there. When there are too many particles, the bleach-like chemicals that white cells use to kill invaders overproduce and destroy air sacs. Once destroyed, they never regenerate. Particles smaller than one micron, (four hundred-thousands of an inch) pass through the air sacs directly into the blood stream and throughout the body.

Breathing fine particles has both short-term and long-term effects in promoting heart disease. Inhaling clean air that is then changed to include fine particles produces marked changes in electrocardiograms and blood chemistry. When heart attacks are simulated in animal subjects, they are greatly amplified in the presence of fine particles. The probability that a defibrillator implanted in a human will need to fire is directly proportional to the amount of fine particles in the air.

Cumulative Damage

Even more deadly is damage to the heart caused by long-term exposure to particles. Once in the lungs, they stimulate nerve fibers, sending signals through the nervous system that change the autonomic balance of the heart. Throughout the cardiovascular system, they stimulate the production of inflammatory agents, which create plaque buildup in the blood vessels and arterial sclerosis. Some particles pass through the lungs and into the blood stream to do direct damage to the heart.

Traffic pollution is especially damaging to children. A study published in the British journal, The Lancet, followed 3,500 children who played sports throughout the year and lived in communities with high ozone levels.[ii] It found that these kids were more than three times as likely to develop asthma as the average population of the same age.

Because a seven-year-old child has many more air sacs per volume of lung, higher metabolism, and is more active than an adult, she will absorb about two and one-half times the air pollutants that her parent does, breathing the same air.[iii]

The resulting permanent reductions in lung function often prevent children who grow up breathing traffic pollution from developing more than 80% of normal lung capacity.[iv] The effect may not be immediately noticeable, because we all start out with more lung capacity than we usually need. But, we lose about 1% of lung capacity per year—1.5% if we smoke. When these kids age and need the extra lung capacity to offset what they have lost, they will not have it.

Even people who have lived near I-93 continuously since its construction have only been exposed to it for 33 years. Although it is chilling to know that our Somerville neighbors suffered 145 excess deaths from 1996 to 2000, the full impact of breathing Somerville air for the past three decades, when known, will be much greater.

[i] Gerald Hoek, Bert Brunekeef, et. al.,“Association between mortality and indicators of traffic-related air pollution in the Netherlands: a cohort study.” The Lancet, vol. 360, October 19, 2003.

[ii] Rob McConnell et. al. “Asthma in exercising children exposed to ozone: a cohort study.” The Lancet, vol 359, February 2, 2002.

[iii] Jonathan Shaw,.“Clearing the Air.” Harvard Magazine, p. 30, May-June 2005.

[iv] W. James Gauderman, Frank Gilliland, Hita Vora, Edward Avol, Daniel Stram, Rob McConnell, et. al. “Association between Air Pollution and Lung Function Growth in Southern California Children: Results from a Second Cohort,” American Journal of Respiratory and Critical Care Medicine. Vol. 165, No. 13, July 1, 2002.