Pesticide exposure and mixture effects in organisms

The extensive use and spread of pesticides in modern conventional farming has been suggested to contribute to the global decline of species, including insect populations. Consequently, pesticides are detected in soil, water and land in agricultural areas. Thus, organisms are chronically exposed to a background level of ill-defined chemical mixtures containing pesticides. Pesticide short term toxicity data is used to assess single substance hazard in risk assessment. However, the consequences of continuous exposure of organisms over generations to low levels of pesticides mixtures remains mostly unknown. Long-lasting exposure may result in sub-lethal effects. In addition, damages might be carried over to the next generations, referred to as epigenetic transgenerational inheritance effects.

In addition to chronic exposure to chemicals persisting in the environment, insects remain seasonal acutely exposed to pesticides resulting from farming activities. In a context of continuous exposure to background level of pesticide mixtures, the question remains to know whether this chronic exposure would affect the susceptibility of organisms to other stressors, i.e. the capacity of the organism to deal with this additional stress. The capacity of insects to react may vary depending on the developmental stage considered and the physiological processes targeted, as metabolic capacities and resources available change between the larval and adult stages.

Pesticides are used everywhere today in modern farming, but how does this effect natural organisms? Today it is unclear how being exposed to several pesticides will cause biological problems for species, for example if it will have long-term effect on reproduction or cause effects for later generations.