In 2010, the Common Sense Alliance (CSA) funded a study that evaluated six soil samples from six residential parcels on San Juan Island. Two additional soil samples were taken from two undeveloped parcels. According to some, this report shows that residential development does not generate pollutants that can negatively impact our wetlands and our fish and wildlife. There are multiple flaws in this CSA-funded study.
Because the frequency and sampling number is very small, this study was excluded from our county’s Best Available Science.
Many of the pollutants that were measured, but not detected in this study, have been banned for decades (DDT, Heptachlor, Aldrin, Dieldrin, Endrin, Methoxychlor, and Chlordane). Endosulfan is primarily used on cotton fields. It is registered for agricultural use -not for residential use. Lindane was banned in 2007 except for medical use for head lice. You would not expect to find Lindane in garden soil.
Testing for Bifenthrin, a pyrethroid pesticide that is used to kill carpenter ants and termites, was not performed. Bifenthrin is routinely applied on the exterior of buildings and on the soil next to the foundation every three months by San Juan Pest Control to prevent insect re-infestations. It is designed to be very persistent, and it is toxic to salmon at extremely low concentrations.
MCPP, an herbicide in “Weed and Feed” products, was detected in soil samples from four out of the six developed residential sites. The presence of MCPP in 66% of the developed residential sites suggests that synthetic chemicals are in common use. This is contrary to some who say, “Don’t worry. Everyone only uses organic methods.”
The samples were taken from locations where most of the analyzed chemicals would be unlikely to accumulate. The root zone of plants breaks down many toxic chemicals into harmless molecules. The timing of application, the amount applied, and the chemical breakdown rate would determine whether the chemical would be detected in the soil under the root zone.
In contrast to this poorly-designed CSA-funded study of soil samples, another study tested for pyrethroid pesticides and surfactants in San Juan County surface waters. This study (Barsh et al. 2008) found significant levels of these pollutants and is included in San Juan County’s Best Available Science. Pulses of surface runoff carry pollutants downhill into our wetlands, lakes, streams, and marine waters. Many critical areas of our marine waters are not well flushed. These include the calmer embayments around which the early settlements were established. Eelgrass meadows are found in calmer waters, and these critical habitats provide nurseries for juvenile salmon and forage fish.
The 2010 Common Sense Alliance-funded study has multiple flaws. Inappropriate sampling sites and methods were used. Widely used toxic chemicals were not analyzed. This flawed study should not be used to claim that residential development does not pollute our critical areas. Instead, the presence of the synthetic chemical herbicide MCPP in the tested residential soil samples shows that organic gardening methods are not as widespread as some are saying.
Janet Alderton Orcas Island