Residential History and Groundwater Modeling: Gallagher et al. Respond

We thank Schaider et al. for their interest in our research on possible environmental causes of breast cancer in upper Cape Cod, Massachusetts (Gallagher et al. 2010). Our study was prompted by an earlier spatial analysis that revealed a geographic overlap between groundwater plumes in upper Cape Cod and an area of increased breast cancer risk. These plumes indicated areas of concern around landfills and wastewater facilities, large point sources of contaminants to groundwater, as shown in Figure 1 of our article (Gallagher et al. 2010). We determined that among these plumes, the plume associated with the Barnstable Wastewater Pollution Control Facility (BWPCF) was the only point source with the potential to impact the drinking water of our study population. The BWPCF treats both residential and commercial waste from a broad geographic area.

occurred through the public supply that was impacted by airport-related VOCs.
A further complication is that Gallagher et al. (2010) stated that they "determined that the BWPCF was the only source of wastewater effluent with the potential to impact the drinking water of this study popu lation"; however, we doubt that.Drinking water supplies of participants in both the exposed and non exposed groups likely contained waste water contaminants originating from septic systems.Among the exposed group, discharges from septic systems contributed substantially to the volume of water pumped from two of the BWPCF-impacted wells (Barlow 1994).Wells serving non exposed participants also were impacted by septic systems.From 1972 to 1985, over half of the public wells in the entire study area contained elevated nitrate concentrations (Silent Spring Institute 2002).In addition, the largest source of groundwater nitrate on Cape Cod is wastewater from septic systems (Brody et al. 2006 and references cited therein).
Despite uncertainty about the composition of drinking water exposures, Gallagher et al. (2010) (Gallagher et al. 2010).Our study was prompted by an earlier spatial analysis that revealed a geographic overlap between groundwater plumes in upper Cape Cod and an area of increased breast cancer risk.These plumes indicated areas of concern around landfills and waste water facilities, large point sources of contaminants to groundwater, as shown in Figure 1 of our article (Gallagher et al. 2010).We determined that among these plumes, the plume associated with the Barnstable Wastewater Pollution Control Facility (BWPCF) was the only point source with the potential to impact the drinking water of our study popu lation.The BWPCF treats both residential and commercial waste from a broad geographic area.
In our study (Gallagher et al. 2010), we applied an extensive ground water model to evaluate historic conditions and determined that effluent from the BWPCF could have reached public drinking water wells as early as 1966.Taking into account residential histories and drinking water source (public, private, and bottled water) among cases and controls, we found an association between Barnstable Water Company (BWC) drinking water impacted by the BWPCF plume and breast cancer that increased with longer latency and greater exposure duration.As Schaider et al. point out, drinking water contamination by private septic systems is ubiquitous in this area.However, because this source of pollution likely affects cases and controls across the entire study area in a similar manner and because the results of a prior study on this topic did not find an association (Brody et al. 2006), this unmeasured source of pollution should not confound the results of our analysis.Nevertheless, we do acknowledge in our article that there may be residual confounding by other unmeasured sources of The correspondence section is a public forum and, as such, is not peer-reviewed.EHP is not responsible for the accuracy, currency, or reliability of personal opinion expressed herein; it is the sole responsibility of the authors.EHP neither endorses nor disputes their published commentary.
environmental contamination, including the Barnstable Airport.We agree with Schaider et al. that these exposures may also contribute to the risk of breast cancer, although the earliest data we are aware of show no appreciable levels of volatile halogenated compounds in 1984 BWC water samples (Janik 1987).With only limited historical data available, we cannot be sure of the exact timing and geographic distribution of these other exposures.However, a very tight correlation would be necessary for these confounders to account for the observed associations with the BWPCF plume, and other exposures would have to date back to 1966.
Fortunately, groundwater sources of drinking water in this area are subject to more protections today, and we agree that on going monitoring of known and emerging contaminants is important to maintain water quality.

Importance of Particle Size-Fraction Analysis in Suspensions
doi:10.1289/ehp.1002354 We would like to comment on the article by Cho et al. ( 2009), which was published in the November 2009 issue of Environmental Health Perspectives (EHP).We read the paper with great interest because the sizedependent effects of particulate matter are very important but have not yet been definitively clarified.In reporting the sizedependent effects of particles, it is essential to know the size distributions of the applied particle solutions, as well as the specific particle size fractions administered.
Cho et al. ( 2009) did not use direct inhala tion exposure, which is the most relevant exposure route for airborne particles (Oberdörster et al. 2005).The particulate matter was sampled, resuspended in methanol and saline, and administered via pharyn geal aspiration to mice (50 µL saline containing 25 or 100 µg particulate matter).Because of the effort required for inhalation studies with size-fractionated airborne particulate matter, the particles were collected and resuspended.However, it is regrettable that the authors did not analyze the size fraction in the suspensions.Particles react in suspensions, especially by forming aggregates, and the reactions are dependent upon the speci fic composition of the suspension liquid (Teeguarden et al. 2007).Therefore, we consider it a signifi cant drawback of the study of Cho et al. ( 2009) that they made statements concerning particulate size effects without taking into considera tion the charac teris tics of the particle suspension used for aspiration.This should have been clearly addressed in the "Discussion" of their article.We are surprised that the reviewers did not highlight this point.
We are interested in studies that take into account the size effects of particles, both  January 22, 2009: 360:376-386 The paper makes an outstanding contribution to the knowledge of environmental epidemiology and was selected because of its quality, originality, importance and expected impact.

Environmental
Health Perspectives • volume 118 | number 9 | September 2010 A 379 ISEE is delighted to announce that its second annual award for the Best Environmental Epidemiology Paper has been granted to C. Arden Pope III, Majid Ezzati, and Douglas W. Dockery for their paper on Fine-Particulate Air Pollution and Life Expectancy in the United States published in New England Journal of Medicine

for Environmental Epidemiology Best Environmental Epidemiology Paper Award for 2009
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