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Common Practice for Monitoring Environmental Impact of Insecticides Deficient, Researchers Say

(Beyond Pesticides, January 15, 2013) Research published in the journal Environmental Monitoring and Assessment calls into question the value of environmental monitoring, such as water sampling, on a fixed date schedule (i.e., once per month), finding that this approach underestimates actual risks. These findings could have a significant impact on how we assess the safety of both endangered species and drinking water supplies.

Researchers explain that, although insecticides are applied less often than herbicides and fungicides, they are usually applied in very large amounts when used in response to acute insect infestations. Scientists found that monitoring for insecticides at pre-set intervals, even weekly or daily, did not detect the occurrence of peak concentrations for these chemicals. Co-author of the study, Ralf Shulz, PhD, explains, “Accordingly, by way of example, on the basis of weekly monitoring of a typical agricultural stream none of the total of six insecticide concentration peaks per year described by model calculations is found. Daily sampling detects only two of the six peaks. Only event-related sampling enables the detection of all these peaks.” Authors of the study point to the need for events-related sampling, both to ensure more accurate detections are taken and to reduce costs. Events-related sampling includes monitoring directly after an insecticide application or heavy downpour. Dr. Shulz continues, “Assuming that the overall costs increase according to the number of fixed-interval samples, on the other hand, the event-related procedure greatly reduces the costs. Furthermore, the benefits are substantially greater. Current practice wastes considerable sums of money, as many of the fixed intervals do not coincide with periods of high insecticide concentrations.”

According to the U.S. Geographical Survey’s (USGS) National Water Quality Assessment (NAWQA), the four most frequently detected agricultural insecticides in U.S. streams are diazinon, carbaryl, malathion, and chlorpyrifos. These highly toxic chemicals are either organophosphate or carbamate class chemicals. All four of these chemicals are extremely harmful to the nervous system, as they are cholinesterase inhibitors and bind irreversibly to the active site of an enzyme essential for normal nerve impulse transmission. Recent research  has shown organophosphates to cause lasting brain damage even at low-level exposure. In addition to contaminating local water supplies, heavy use of these toxic insecticides can result in significant harm to sensitive or endangered species. Large influxes of these chemicals can have a homogenizing effect on the composition of aquatic communities, in effect reducing ecological diversity and allowing the intrusion of opportunistic species.

The study adds a considerable layer of doubt to current resource monitoring methods. For instance, if a sample is taken at the wrong time it may reveal no detection when in fact the waterway may be under heavy pollution loads. Lead author of the study, Sebastian Stehle, PhD,  notes, “The values resulting from this sampling therefore give a completely false picture of the true impact of insecticides. Including results in the evaluation according to which no pollution has been detected distorts the evaluation and simulates a false sense of safety. Samples showing no evidence of insecticide pollution should therefore not be considered — at least as long as environmental impact monitoring takes place statically. Still better would be event-related sampling, at least in high-risk areas.”

Pesticides in waterways have been attributed to the feminization of male amphibians, and intersex fish- male fish producing eggs in the Potomac. Studies link increased seasonal concentration of pesticides in surface water with the peak in birth defects in infants conceived during the spring and summer months, when pesticide use increases and high concentrations of pesticides are found in surface waters. A 2009 report by the Natural Resources Defense Council (NRDC), Poisoning the Well, found that atrazine goes undetected by regular monitoring, and in the 139 municipal water systems from which EPA collected data on a biweekly basis in 2003 and 2004, atrazine is found 90% of the time. Furthermore, 54 of these water systems had at least one spike above 3 parts per billion, atrazine’s current benchmark. Atrazine in drinking water was recently linked to menstrual irregularities in women.

Although EPA released new human health benchmarks for acute pesticide effects in drinking water last spring, the agency’s step forward falls short as these rules are voluntary guidelines without any enforcement mechanism. The new benchmarks fail to evaluate concerns resulting from chemical mixtures, synergistic effects, and health impacts associated with chronic low-dose exposure. Moreover, if highly toxic chemicals are entering U.S. waterways and not being detected by regular monitoring, Dr. Stehle’s research highlights another significant gap in our regulatory process, which puts both human health and the environment at risk.

In light of this important revelation, researchers laid out several cost-efficient ways to reduce overall contamination in waterways near farms. This includes simple practices such as widening border strips between farm and water resources, and edging fields with hedges in order to reduce spray drift. Apart from reducing pesticide contamination, Dr. Shulz notes, “…with these measures agriculture can make a very important positive contribution to the protection of nature and biodiversity in a ‘culture landscape of the future’.”

Organic farming is already taking this important step towards protecting and strengthening the natural landscape. Included within the Organic Foods Production Act  is a requirement to foster soil fertility through proper management practices. Organic food contributes to better health through reduced pesticide exposure for all and increased nutritional quality. In order to understand the importance of eating organic food from the perspective of toxic pesticide contamination, we need to look at the whole picture —from the farmworkers who do the valuable work of growing food, to the waterways from which we drink, the air we breathe, and the food we eat. Organic food can feed us and keep us healthy without producing the toxic effects of chemical agriculture. For more information on Organic Food see our program page, and for additional information on water contamination see our program page on Threatened Waters.

Source: ScienceDaily Press Release

All unattributed positions and opinions in this piece are those of Beyond Pesticides.


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