Environmental Factor, August 2006, National Institute of Environmental Health Sciences
DERT Papers of the Month
By Jerry Phelps
More Evidence for Parkinson's Disease and Pesticide Link
A large epidemiologic study shows that individuals reporting regular exposure to pesticides had a 70 percent higher incidence of Parkinson's disease than those reporting no exposure. The study, funded by NIEHS and conducted by researchers at the Harvard School of Public Health, is the first large-scale prospective study to examine the possible links between chronic pesticide exposure and Parkinson's disease.
Previous studies suggested pesticide exposure as a risk factor for the dreaded neurological disorder. However, the results were inconclusive because of the relatively small numbers of participants. The current study included more than 143,000 subjects; 7,800 reported exposure to pesticides. No increased risk for Parkinson's disease was found from other occupational hazards including exposure to other chemicals or solvents.
Research utilizing twins has established that genetics probably plays a minor role in Parkinson's disease and thus has made environmental exposures the focus of much interest. A compound known as MPTP, a by-product of the production of a heroin-like illicit drug and structurally similar to the herbicide paraquat, causes death of neurons in the substantia nigra, the part of the brain affected by Parkinsons's disease. For that reason, pesticide and herbicide exposures are considered likely to cause or contribute to the development of Parkinson's disease.
Citation: Ascherio A, Chen H, Weisskopf MG, O'reilly E, McCullough ML, Calle EE, Schwarzschild MA, Thun MJ. Pesticide exposure and risk for Parkinson's disease. Ann Neurol. 2006 Jun 26; [Epub ahead of print]
DNA Damage in Fish as Biomarkers for Exposure and Effects of Organic Pollutants
Identification of DNA damage in the liver and gills of native fish can serve to detect exposure to, and effects from, pollutants found in the environment, according to research from the Pacific Northwest Research Institute, Woods Hole Oceanographic Institution, the University of Maryland and the National Institute of Standards and Technology. The findings also suggest that these biomarkers can be used to track progress in cleaning up environmental contamination.
Researchers analyzed fish from two sites in Washington State. They compared English sole from the Duwamish River, which flows through an industrialized section of Seattle, to the same species taken from Quartermaster
Harbor, a relatively clean area in the Puget Sound. A section of the lower Duwamish River was listed as an EPA Superfund Site in 2001. Chemicals contaminating the river bed include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, mercury and other metals, and phthlates used in making plastics.
The river fish had higher levels of "deleterious alterations" in DNA isolated from their livers and gills than the harbor fish. The river fish also had higher levels of gene expression for the enzyme cytochrome P4501A, which "signaled changes in the liver associated with the oxidation of organic xenobiotics." The researchers conclude that these and similar DNA lesions can be used to detect impacts of chemical contaminants on fish populations. And since innate DNA repair processes can reverse previous damage as long as additional insults don't occur, they may be useful in assessing the effectiveness of environmental remediation efforts.
Citation: Malins DC, Anderson KM, Stegeman JJ, Jaruga P, Green VM, Gilman NK, Dizdaroglu M. Biomarkers signal contaminant effects on the organs of English sole (Parophrys vetulus) from Puget Sound. Environ Health Perspect. 2006 Jun;114(6):823-9.
Allergy and Respiratory Infections in Infants - Effects of Tobacco Smoke, Mold, and Older Siblings
Exposure to environmental tobacco smoke increases an infant's risk of developing allergic rhinitis by almost three-fold, report NIEHS grantee Grace LeMasters and trainee Jocelyn Biagini in the June issue of Pediatric Allergy and Immunology. The epidemiologic study was conducted with a group of 633 infants less than one- year of age and is the first to show the relationship between exposure to tobacco smoke and allergy in this age group. The researchers also found that exposure to mold in the home is associated with increased risk of upper respiratory infections but not allergy, which differs from previously reported research in older children and adults.
Other findings include a protective effect of having older siblings in the home. Infants with at least one older sibling were less likely to have allergic rhinitis, also known simply as hay fever, by their first birthdays. This finding supports the "hygiene hypothesis,' a theory that exposure to infectious agents early in life may decrease the risk for allergic diseases such as asthma later in life. Presumably by having older siblings, these infants were exposed to a wider variety of viruses and bacteria, causing their immune systems to develop in a way that decreases the risk of allergy.
About one-fifth of all American adults smoke cigarettes resulting in about 43 percent of children being exposed to home environmental tobacco smoke. Further research is necessary to confirm these results and to determine the components of cigarette smoke that cause the effects.
Citation: Biagini JM, Lemasters GK, Ryan PH, Levin L, Reponen T, Bernstein DI, Villareal M, Khurana Hershey GK, Burkle J, Lockey J. Environmental risk factors of rhinitis in early infancy. Pediatr Allergy Immunol. 2006 Jun;17(4):278-84.
Asthma in Elementary School Children is Associated with Proximity to Concentrated Animal Feeding Operations
Elementary school children may be at higher risk for developing asthma if their school is near a large-scale livestock farm known as a concentrated animal feeding operation (CAFO), according to research published in the June issue of Chest, the journal of the American College of Chest Physicians. Joel Kline, an NIEHS-supported scientist at the University of Iowa Environmental Health Sciences Research Center, studied children at two rural Iowa elementary schools. The study school was a half mile from a CAFO and the control school was more than 10 miles away from any large-scale agricultural facility. Almost 20 percent of children at the study school had a physician-diagnosis of asthma compared to about 7 percent of the control school kids.
When Kline broadened the definition of asthma to include asthma-like symptoms or asthma medication use, there was still more than a two-fold difference in the asthma prevalence. The overall rate of physician diagnosed asthma in Iowa is 6.7 percent.
CAFOs are controversial because of recurring problems with odor, ground and surface water contamination, and noise. According to Kline, they emit irritants and inflammatory substances that affect the health of workers at the facilities and are a detriment to air quality in surrounding communities. Prompted by these findings, he designed the current study to investigate whether there was a connection between CAFOs and increased rates of asthma among children in rural areas.
The paper urges caution on the interpretation of the results. Possible confounders of the study could be differences in smoking rates among the children's parents, pet ownership, residence on a farm, asthma diagnosis by different physicians, etc. The authors conclude that more research is necessary on the effects of CAFOs on communities, not just on workers or people in the direct vicinity of the facilities.
Citation: Sigurdarson ST, Kline JN. School proximity to concentrated animal feeding operations and prevalence of asthma in students. Chest. 2006 Jun;129(6):1486-91.