Pesticide residue monitoring: keeping up with constant change

Pesticides greatly improve crop yield and feed an ever-growing human population. However, all around the world, there is a continuous flow of information about the damage that pesticides and their residues can do to people, their foods, and the environment. With companies like DuPont and BASF also driving change by introducing new, more robust products onto the market, regulators around the world are being pushed to constantly tweak and update the rules on how pesticides can be used. This, in turn, gives analytical laboratories an essential, three-part safeguarding role: assessing safety thresholds, monitoring the extent of contamination, and helping ensure that those employing pesticides follow the rules.

First finding its voice with the publication of Rachel Carson’s anti-pesticide exposé Silent Spring in 1962, the modern environmental movement has successfully harnessed the power of activist groups, scientific research, and influential media organisations to spread its message about the dangers of pesticides and other contaminants. A number of recent studies about pesticides’ detrimental effects have been widely reported – such as a survey of 2,000 hectares of farmland in the UK, Germany and Hungary which confirmed that neonicotinoid pesticides (NNIs) “negatively affect pollinator health under realistic agricultural conditions”. And in May, a report from more than 50 researchers using a uniquely large dataset named pesticide use as a key factor behind huge reductions in bird numbers across Europe. “Agricultural intensification, in particular pesticides and fertiliser use, is the main pressure for most bird population declines, especially for invertebrate feeders,” it concluded. The authors also argued that “the highest political and technical challenge faced by agricultural policy… (is) to balance high productivity from intensive agricultural practices with environmental protection.”

In Europe, the campaign against neonicotinoids has already led to bans on farmers using imidacloprid, clothianidin, thiamethoxam, and thiacloprid, while the US debate on whether to follow suit has raged for several years – with an EPA registration review of five NNIs now due to conclude next year. The Biden administration - which showed itself willing to make big calls on pesticides when it followed Europe and banned chlorpyrifos on all US foods in 2021 - is again under pressure to do the same with NNIs, especially as New York, New Jersey, Maryland, Maine, and Connecticut have already imposed their own restrictions on non-agricultural use.

Just as pesticide use and contamination is a live global issue, changes to pesticide regulations are happening all the time, all over the world. For example, India has recently announced new maximum residue limits (MRLs) for pesticides used on tea plants – including emamectin benzoate, fenpyroximate, hexaconazole, and propiconazole. Last year, South Korea introduced a national ‘positive’ MRL list for pesticide residues in imported foodstuffs, and has also revised its pesticide tolerance standards for agricultural products. Meanwhile, Japan is changing its own MRLs for spinosad, sulfoxaflor, pyraflufen-ethyl, and  benthiavalicarb-isopropyl.

Analytical scientists working for governments and regulatory authorities also continually monitor pesticide residues in foods already on the market – with the latest reports from US, EU, and UK laboratories all confirming that that the vast majority of food samples tested met safety standards. However, for the first time in its history, Europe’s Rapid Alert System for Food and Feed (RASFF) named pesticides as its most-reported hazard – adding that “notifications for imported food regarding unauthorised pesticides have soared.” In 2020, RASFF also had to deal with a major food contamination scandal linked to sesame seeds from India that contained up to 200 times the permitted MRLs of the banned and potentially genotoxic pesticide ethylene oxide (EtO). The findings have since led to the recall of more than 3,000 food products and a subsequent clampdown on using EtO in food additives, as well as a widening of the range of foods that must be tested. In this ever-changing testing environment, testing laboratories need high-quality, reliable and up-to-date reference materials that help give them confidence in the integrity of their methods and results.  The Dr Ehrenstorfer portfolio of pesticide reference materials exists precisely to meet that need, and to help provide that assurance.