Dear EarthTalk: Are my kids breathing in dangerous exhaust fumes by riding the school bus?
—Molly Schink, Winnetka, IL
Over 24 million children ride the bus to school every day and as a result are regularly exposed to harmful diesel exhaust emissions. Major components of diesel exhaust include carbon monoxide, sulphur dioxide, formaldehyde and tiny soot particles that carry substances called polynuclear aromatic hydrocarbons.
The U.S. Environmental Protection Agency (EPA) classifies diesel emissions as a "likely carcinogen." Diesel emissions are estimated to be responsible for 70 percent of the cancer risk arising from air pollution, according to the California Air Resources Board. Dangers from diesel exhaust can range from respiratory illnesses including asthma and bronchitis to lung cancer and heart disease.
Children are more vulnerable to the effects of diesel exhaust than adults because they breathe more quickly and take more air into their developing lungs. And on average, school children who ride the bus spend an average of 90 minutes each weekday in transit.
The EPA estimates that approximately 390,000 diesel school buses are on the road in the U.S. today. A third of these were made before 1990 when stricter emissions guidelines were first enforced. According to the National Resources Defense Council (NRDC), a child riding inside a school bus may be exposed to as much as four times the amount of toxic diesel fumes as someone riding in a car directly ahead of it.
Recently, the EPA pledged more than $1 million to a partnership called the Northeast Diesel Collaborative, which is comprised of eight different public and private entities working together to improve emissions on thousands of school buses throughout the northeastern U.S. Recipient groups are using the money primarily to reduce emissions on older buses by installing advanced pollution controls.
Retrofitting old buses with such controls involves installing emissions reducing filters. Diesel particulate filters, which cost around $700 each, can cut tailpipe emissions by a whopping 85 percent. And "closed crankcase filtration systems," which are installed under the hood and filter the discharges that come directly from the engine's crankcase vent, can cut engine soot by nearly 90 percent at a cost of around $7,500 each. Buses can be retrofitted with one or both filters.
Nationwide a number of school bus emission-reduction programs are underway with the help of the EPA's Clean School Bus USA program. In addition to retrofit projects the program seeks to replace older buses with new less polluting buses and encourage unnecessary school bus idling.
Concerned parents can help reduce their children's expose to diesel emissions from school buses by advocating at town and boards of education meetings for the use of new or retrofitted school buses. Also, bus windows should remain open when weather allows, and children are safer sitting nearer the front of the bus, as exhaust tends to accumulate in the back.
Dear EarthTalk: What is "light pollution?" Is it really a factor in breast cancer?
—Gudrun Smythe, Madison, Wisconsin
The glow of city lights blotting out stars in the night sky has frustrated many a stargazer, but recent studies have shown that "light pollution"—defined as excess or obtrusive light at night—can actually have serious health effects. Researchers have found that exposure to bright nocturnal light can decrease the human body's production of melatonin, a hormone secreted at night that regulates our sleep-wake cycles. And decreased melatonin production has in turn been linked to higher rates of breast cancer in women.
"Light at night is now clearly a risk factor for breast cancer," says David Blask, a researcher at the Cooperstown, New York-based Mary Imogene Bassett Research Institute. "Breast tumors are awake during the day, and melatonin puts them to sleep at night," he adds.
Epidemiologist Richard Stevens of the U.S. Department of Energy's Pacific Northwest National Laboratory first discovered the link between breast cancer and light pollution in the late 1980s. Stevens found that breast cancer rates were significantly higher in industrialized countries, where nighttime lighting is prevalent, than in developing regions.
Lending credence to Stevens" research are the findings of another researcher, William Hrushesky of the South Carolina-based Dorn Veterans Affairs Medical Center, who discovered that female night shift workers have a 50 percent greater risk of developing breast cancer than other working women. He also found that blind women have high melatonin concentrations and unusually low rates of breast cancer.
To reduce breast cancer risks from light pollution, Prevention magazine recommends nine hours of sleep nightly in a dark room devoid of both interior (computer screens) and exterior (street lamps) light sources. A study of 12,000 Finnish women found that those who slept nine hours nightly had less than one-third the risk of developing a breast tumor than those who slept only seven or eight hours. Even bright light from a trip to the bathroom can have an affect, so dim nightlights are recommended for night lighting.
Light pollution causes other problems besides increased cancer risks. According to the Sierra Club, birds and animals can be confused by artificial lighting, leading them away from familiar foraging areas and disrupting their breeding cycles. And the photosynthetic cycles of deciduous trees (those that shed their leaves in the fall) have been shown to be disrupted due to the preponderance of artificial nighttime lights.
Another environmental impact of excessive use of artificial light is, of course, energy waste. The International Dark-Sky Association computes that unnecessary nighttime lighting wastes upwards of $1.5 billion in electricity costs around the world each year while accounting for the release of more than 12 million tons of carbon dioxide, the leading greenhouse gas, into the atmosphere. Individuals can do their part by keeping lights dim or off at home at night—and convincing their employers and local government offices to do the same.