Journal of Toxicology Study Reviews Carcinogenic Outcomes and Associated Results from Exposure to Two Common Lawn Care Chemicals

John Heinze, PhD

Journal of Toxicology Study Reviews Carcinogenic Outcomes and Associated Results from Exposure to Two Common Lawn Care Chemicals

CHANTILLY, Va., September 5, 2012— The August issue of the Journal of Toxicology includes a report by Katherine von Stackelberg, Sc.D. on human exposure to two common lawn care chemicals 2,4-D, and MCPA.   Both 2,4-D (2,4-Dichlorophenoxyacetic acid) and MCPA (2-methyl-4-chlorophenoxyacetic acid) are herbicides used to control broad leaf weeds.

Katherine von Stackelberg, principal of E Risk Sciences and a research manager at the Harvard Center for Risk Analysis, selected the two compounds because of their wide use as herbicides in the United States for both agricultural and residential applications.  This study follows von Stackelberg’s earlier review on exposure data for bifenthrin, and azoxystrobin where she concluded, “Significant research has been done on these products and the weight of evidence indicates very little potential for adverse health effects associated with environmental exposures.”

In the Journal of Toxicology article, A Systemic Review of Carcinogenic Outcomes and Associated Mechanisms from Exposure to Concentration of 2,4-D and MCPA in the Environment, von Stackelberg set out to determine whether there was any validity to the suggestion from some epidemiologic studies that both 2,4-D and MCPA may be associated with an increased risk of non-Hodgkin’s lymphoma (NHL), Hodgkin’s disease, leukemia, and soft tissue sarcoma.

She noted that toxicological studies in rodents show no evidence of carcinogenicity and that health protection agencies worldwide consider the compounds as not likely to be carcinogenic or unclassifiable as to carcinogenicity.

Dr. von Stackelberg did a systemic review assembling available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between environmentally-relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers.

In her report, von Stackelberg noted that given that the RfD (EPA’s reference or “safe” dose) is a dose associated with no effects (including a margin of safety), and that cell culture bioassay results may not translate into live animal effects, “the combined evidence indicates it is highly implausible that exposure to 2,4-D and/or MCPA are associated with a risk of developing NHL or other lymphohematopoietic cancers.”

In her abstract, Dr. von Stackelberg concludes, “The combined evidence does not support a genotoxic mode of action.  Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship.”

“I wouldn’t hesitate to let my children and dogs play on a lawn where lawn care products have been used,” stated Katherine von Stackelberg, Sc.D, “as long as the products were applied according to their respective labels.” As part of a series of studies commissioned by the Environmental Health Research Foundation, von Stackelberg selected four of the most commonly used lawn care products and reviewed 2,4-D and MCPA them to evaluate the strength of the association between exposure and potential health effects.   She reviewed the toxicological, epidemiological, and exposure data for bifenthrin, azoxystrobin, 2, 4-D and MCPA (a member of the same chemical family as 2,4-D).

“Significant research has been done on these products,” von Stackelberg explained, “and the weight of evidence indicates very little potential for adverse health effects associated with environmental exposures.”    The U.S. Environmental Protection Agency carefully monitors and approves lawn care products for use.  Over the years, it has eliminated questionable products from use on lawns.  As part of the pesticide registration process, U.S. EPA evaluates and in some cases conducts independent research to evaluate potential risks and define acceptable uses. They have determined there is little or no health risk associated with exposure to bifenthrin, azoxystrobin, 2,4-D and MCPA—when the products are used as directed.

“Green space, particularly in urban areas, offers significant health benefits, which are described in the Environmental Health Research’s review of the literature.  Maximizing these benefits may require the use of products to ensure a healthy, thriving green space, and the goal is to use products with the greatest efficacy and the least potential for risk,” stated von Stackelberg.

The Environmental Health Foundation has a report available online which reviews all of the literature on the benefits of green space.  With this report, EHRF produced a comprehensive bibliography of current university and governmental research which outlines the importance of healthy lawns.  From erosion control to water and air purification to carbon sequestration to increasing home values the research shows that healthy lawns provide important environmental benefits as well as help create the kind of ideal play surfaces that can help stem the problems associated with the growing epidemic of childhood obesity.

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About Katherine von Stackelberg

Katherine von Stackelberg is principal of E Risk Sciences and a research manager at the Harvard Center for Risk Analysis.   E Risk Sciences specializes in developing risk-based modeling tools to support environmental decision making. Much of von Stackelberg’s work has focused on incorporating quantitative uncertainty analysis (e.g., analytical, probabilistic and fuzzy methods) into the risk assessment process and she has been at the forefront of the effort to promote uncertainty analysis and methods for communicating uncertainty to support environmental decision-making.  She has spent more than twenty years developing risk-based approaches to support sustainable decision making. An emerging focus area for von Stackelberg is developing tools and methods to evaluate ecosystem service tradeoffs associated with environmental management decisions. She serves on the U.S. EPA Board of Scientific Counselors, and is a member of the Scientific Advisors on Risk Assessment for the European Commission in Brussels. She is also a Research Manager at the Harvard Center for Risk Analysis and is the Co-Director of the Superfund Research Translation Core. She received an A.B. cum laude from Harvard College, and a Sc.M. and Sc.D. from the Harvard School of Public Health in Environmental Science and Risk Management.  She also serves as a consultant to the Environmental Health Research Foundation.

About EHRF

The Environmental Health Research Foundation (EHRF) is a nonprofit, nonpartisan scientific research foundation seeking to improve the analysis and communication of health and environmental science. Its goal is to further the understanding of science related to health and the environment, and especially the interaction between the environment and human health. EHRF Executive Director John Heinze, PhD brings over 20 years of research, management, and communications experience to the EHRF. In addition to his expertise in microbiology, molecular biology, genetics, and toxicology, Heinze has authored over 35 scientific papers and presentations to international conferences and workshops. Since 1995, Heinze has served as a senior science adviser on health and environmental issues, including the communications aspects of such issues. A particular focus has been on communication of health and environmental safety information including activities ranging from those focused on single substances to broad issues affecting numerous materials.