80% of pesticides found in sediments exceed regulatory thresholds, international study finds

(NaturalNews) Freshwater sources worldwide are so heavily contaminated by pesticides that 80 percent of sediment tested at levels that exceed the maximums set by government regulators, according to a study conducted by researchers from the University of Koblenz-Landau and published in the Proceedings of the National Academy of Sciences.

In the United States, European Union, and many other countries, the process of granting government approval to a pesticide involves setting a "regulatory threshold level" (RTL) for that chemical's concentration in the environment. Theoretically, the RTL is the level at which a chemical will not cause detrimental effects, although in practice, some chemicals are toxic even at their RTL. The RTL is based on laboratory tests of the pesticide's toxicity.

High levels of contamination widespread

The researchers performed a meta-analysis of 838 prior peer-reviewed studies on the concentration of insecticides in a total of 2,500 surface water sites located in 73 separate countries. The studies included a total of 28 pesticides, nearly all of which are authorized for use in the European Union or United States. Samples were collected between 1962 and 2012.

Of the 11,300 pesticide samples taken, more than half were found to exceed RTL levels; this occurred in 68.5 percent of locations tested. In some cases, pesticides were found at concentrations of 10,000 or more times the RTL.

More specifically, 40 percent of water samples detected pesticides at higher-than-RTL levels, while such levels were found in a shocking 80 percent of sediment samples from the bottom of the water.

The researchers sought to determine whether the problem was worse in poorer African or Asian countries, which tend to have less government regulation than wealthier countries. They found almost no difference: 42 percent of insecticides were found at higher-than-RTL levels in poor African or Asian countries, compared with 40 percent in wealthy countries such as the United States, European Union, Australia, Canada and Japan.

They also found that contrary to assertions that pesticide regulation has improved, newer pesticides were actually more likely to exceed RTLs than older ones.

Study actually underestimates the problem

The researchers warned that the problem is probably far worse than the raw data suggests. That's because only about 10 percent of the world's agricultural surface waters were included in the study. Additionally, pesticide contamination of freshwater in agricultural regions tends to be seasonal, with periodic spikes that last only a few days and are therefore hard for scientists to detect. Studies have shown that these brief spikes can have devastating effects on aquatic ecosystems.

Furthermore, more than 80 percent of the samples analyzed tested positive for more than one pesticide; in some cases, as many as 30 were detected. Scientists know that exposure to multiple pesticides can produce effects drastically worse than the sum of the individual exposures, but they remain mostly ignorant of the details of these interactions. Government regulatory processes, in contrast, tend to ignore interaction effects entirely.

Finally, any focus on RTLs will intrinsically understate the nature of the ecological threat posed by pesticide contamination because RTLs are almost uniformly set too high. In the current study, the researchers found that even when pesticides occurred only at the RTL, they caused a 30 percent drop in freshwater biodiversity. Other studies have confirmed that aquatic life is particularly vulnerable to the effects of pesticides, often at levels far below the RTL.

The study shows that the system in place for regulating pesticides is too weak and is fundamentally flawed, the researchers said. This poses a serious threat to global biodiversity.

"Overall, our analysis suggests that fundamental revisions of current regulatory procedures and pesticide application practices are needed to reverse the global environmental impacts of agrochemical-based high-intensity agriculture," they wrote.

(Natural News Science)




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