A growing concern

Abstract

In early April, the US Environmental Protection Agency (EPA) backed down from a planned, but perhaps poorly conceived, if not unethical, study on the effects of pesticides on children, when two senators threatened to block the confirmation of Stephen L Johnson as EPA Administrator. Unfortunately, the negative press EPA received from the incident overshadowed a more positive step the agency recently took to protect children. In late March, EPA released its first update since 1986 on cancer risk from environmental pollutants. A long time in coming, the new Guidelines for Carcinogen Risk Assessment and Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens, is influencing new regulations on chemicals found in air, water, pesticides, and waste, and the cleanup standards for Superfund and hazardous waste sites. More specifically, they recommend principles and procedures to guide EPA scientists and others in determining the cancer risks from exposure to chemicals or other agents in the environment. They are also used to inform EPA administrators and lawyers, state governments, and the public about risk assessment procedures. Environmental groups are applauding what they see as a promising change in EPA policy. The additional Supplemental Guidance describes approaches that EPA could use to assess children's cancer risks from harmful chemicals. This is the first time that a risk guidance document specifically related to children has been issued by the EPA. It includes a review of scientific literature on chemical effects in animals and humans and summarizes the results of the cancer studies that investigated early-life exposure. Over 10 years ago, the National Research Council (NRC) recommended that “EPA assess risks to infants and children whenever it appears that their risks might be greater than those of adults”. This pronouncement has finally been heeded. The original Guidelines for Carcinogen Risk Assessment was published in 1986, and was based on assumptions by toxicologists that if a substance caused cancer in an animal, it would also cause cancer in humans. Those assumptions resulted in many valuable and scientifically valid discoveries regarding childhood exposure to such pollutants as residential lead paint. Yet recent advances have led EPA to determine that in some cases substances harmful to animals do not necessarily pose risks for humans. More startling are newer studies demonstrating that some substances, such as benzene, may be more harmful to humans than once thought. One key portion of the Supplemental Guidance points out that recent advances demonstrate the differences between adults and young children when exposed to carcinogenic chemicals, recognizing the possibility that children under 2 years might be ten times more at risk and children from two to 16 might be three times more at risk. There is a lot of information suggesting links between childhood chemical exposure and a number of diseases. Children are thought to be more susceptible to the health effects of air pollution because their immune systems and developing organs are still immature. Exposure to toxic air contaminants during infancy or childhood could affect the development of the respiratory, nervous, endocrine, and immune systems and increase the risk of disease later in life. Researchers from the University Medical Center and the Nicholas School of the Environment and Earth Sciences at Duke University recently concluded that seasonal variations in the use of pesticides, fungicides, other water pollutants, and antihistamines could expose fetuses to these compounds during critical periods of brain development, perhaps contributing to brain cancer. A new study at Columbia of 60 newborns in New York City revealed that prenatal exposure to combustion-related urban air pollutants alters the structure of chromosomes of fetuses in the womb. Environmental exposure to such pollutants during pregnancy, the study hypothesizes, causes a modest a modest but significant increase in chromosomal abnormalities in fetal tissues. Such genetic alterations have been linked in other studies to increased risk of cancer in children and adults. While the applause for EPA's new report was audible, not all environmentalists are happy about the approach. The National Resources Defense Council commented that the efforts to consider all available science to reduce the risk of cancer were laudable, but they contrast this with EPA's approach to solving other problems, especially the halfhearted effort to reduce mercury emissions from coal-fired power plants. The new mercury regulations use a cap-and-trade program as opposed to the Clinton-era approach, which forced plant operators to use the best technology available. New lawsuits and petitions will contest that rule. Power plants emit elemental mercury and mercury oxides. When these enter the food chain, both become methyl mercury, which damages the central nervous system – especially in young children. So even if, as the old adage says, “children should be seen and not heard”, it is high time that environmental science paid them some attention. Douglass F Rohrman