Addressing Pesticide Residue

In addition to de-listing existing compounds, the EFSA has the responsibility to ensure that new plant protection products are fully evaluated for safety, efficacy and environmental impact prior to being made available to growers.

In 1993, a survey by the National Resources Defense Council found that worldwide there were 71 pesticides used on food crops that have been found to cause cancer in animals and humans. Similar concerns regarding organo phosphorus and carbamate compounds are being expressed in campaigns led by Greenpeace and Friends of The Earth. A number of these compounds, developed as many as 50 to 60 years ago, have been taken off the markets both in the U.K. and the U.S., and replaced by compounds, which have better activity or less environmental or potential human health impact. The list of approved pesticides, herbicides and fungicides is long and growing as new compounds are introduced and used (or misused) by growers looking for more effective options.

Against this background, the requirements for reliable, sensitive and comprehensive analysis of pesticide residues in food has never been more crucial to ensure compliance with national and international law and to assure consumers that their fruits and vegetables are healthy.

New Detection Techniques

Traditionally, pesticide residues in foods were monitored with multi-residue methods such as gas chromatography (GC) coupled with either selective detectors or mass spectrometry (MS). But the newer substances, while safer, have proved difficult to monitor because they are either not amenable to GC or are not detectable at sufficiently low levels to assess their compliance with statutory maximum levels.

In order to keep up with the changing landscape, companies providing agricultural analysis in Europe have had to shift to new detection techniques to measure the residue of the recently approved pesticides. One response has been for the produce testing labs to assay compounds separately with individualized methods for each class; but this results in lengthy analysis times with high staff and consumables cost.

With the emergence of new compounds on the market and a reduction in allowed MRLs throughout Europe, companies that provide full-scale analysis and consulting on food products, such as Law Labs, (Birmingham, England) have seen an increase in the demand for their services. Law Labs works with a number of the largest worldwide agricultural suppliers as well as supermarket retailers to independently test and validate the pesticide levels in traded and marketed produce and other foodstuffs.

“This isn’t just about needing to test for many more compounds, it’s also about being able to test them at lower and lower levels,” says Don Brown, pesticide services manager for Law Labs. “The challenge is being able to achieve these detection levels with a high degree of confidence so you are certain that what you have identified is genuinely a pesticide, not a co-extracted artifact.”

Brown, who belongs to the Royal Society of Chemistry, the Institute of Food Sciences and Technology and the British Mass Spectrometry Society, been testing food for pesticides for more than 20 years. He is a stickler for both accuracy and validity and emphasizes that “for routine testing it is necessary to be able to detect to a level that is at least half of what is set for compliance so you know that you are well within the maximum limits.”

He notes that until recently, the company had established systems for detecting common pesticides, but only a piecemeal approach for the analysis of novel substances that were not amenable to identification by GC-MS. One approach used was to apply different GC conditions or combined liquid chromatography (LC) with UV or fluorescence detection on these odd samples, but this would often require separate extractions of the same sample and was not an efficient solution.