Next time you walk up and down the aisles of your favorite supermarket, think about this—on average 35 percent to 40 percent of all food and fiber crops grown around the world are lost to pests and disease every year. As food safety and risk management professionals, we can all readily appreciate the importance of pesticides in preventing potential food shortages or worse. In fact, pest control dates back to the first person to swat a bug. More methodical methods soon followed. The Sumerians used a sulfur compound to drive off insects. The Egyptians had over 800 recipes for pesticides, while the Chinese used arsenic and mercury compounds to control plant diseases and fend off pests.
The Ubiquity of Pesticides
Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, and various other substances used to control pests. Today, more than 5.5 billion pounds of these chemicals are applied to seasonal crops around the world each year. The U.S. agricultural industry alone uses over half a billion pounds of pesticides a year to treat just 21 selected crops, including corn, soybeans, and wheat. According to USDA, about 76 percent of those pesticides are herbicides, 17 percent are soil fumigants, desiccants, and plant growth regulators, while insecticides account for the remaining 7 percent.
With all of those chemicals ending up on global crops, it should come as no surprise to learn that trace amounts of those chemicals end up in the food supply. Remember your mom always telling you to wash that fruit or vegetable before eating it? Turns out she was right. Residual pesticides are found in 52 percent of fruits and over 30 percent of vegetables. But even mom’s advice does not often help, since washing foods does not always remove all of the chemicals. Beyond those that cling to the skin of fruits, vegetables, and grains, some are actually absorbed into the food itself. Despite all of the preventive measures in place, consumers are still eating pesticides on a daily basis.
Even more disturbing is the potential accumulative effects of longtime exposure to these chemicals. The possible implications of exposure to multiple pesticides on food are also of growing concern. It is not uncommon, for instance, to treat crops several times with different pesticides depending upon treatment needs, including insects, rodents, fungi, and soil enhancers. One recent study linked multiple myeloma to certain agricultural exposures, including pesticides, in men throughout North America. Another recent ruling in California will soon require a cancer warning to appear on glyphosate, the world’s most popular weed killing pesticide.
Preventive Measures Abound
In most countries pesticides are highly regulated and designed to dissipate by harvest time, leaving behind only trace amounts of compounds that are measured in the parts per million and billion (ppm and ppb) levels. Government regulators note that those levels are below the legal tolerance limits set by food safety agencies from around the developed world, and are thus safe for human consumption. In every instance, these tolerance levels already factor in an added safety margin that considers their potential impact on children, who consume more food by body weight, as well as people with higher sensitivities.
In order to verify these tolerance standards, farmers, food manufacturers, processors, packagers, and some larger grocery chains now conduct their own testing to make sure every ingredient is within the established tolerance limit. In states like California, which has the strictest standards for pesticide use, testers are mandated by law to fully describe or reference the preparation process and methodologies used as well as provide validation data and all analytical reports upon request.
What do most testing laboratories use to detect, identify, and quantify pesticides in food? While there are multiple methods to measure pesticides at environmentally relevant concentrations, the industry gold standard is chromatography. Both gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) meet the analytical requirements to detect pesticides in food, especially in fruits and vegetables.
GC/MS. This is a highly sensitive and universal detecting system that most people encounter at airports, where it is used to detect substances in luggage or on passengers. Able to detect trace elements down to ppm and ppb, which appear as chromatographic peaks on a chromatogram, GC/MS is frequently used to detect a wide variety of analytes within a single sample matrix, such as pesticide residues in food. GC/MS can also be used to help identify unknown pesticide elements by comparing their relative retention time data to that of a standard, such as chlorpyrifos that is typically used as the standard for common chlorinated hydrocarbon and organophosphate pesticides.
LC/TOF-MS. A newer, more sensitive, and faster technology for pesticide analysis is liquid chromatography/time-of-flight mass spectroscopy, or LC/TOF-MS. Basically, the system determines an ion’s mass-to-charge ratio by measuring the time it takes for an ion to reach a detector that is set at a predetermined distance. That time measures the ion’s velocity and is used to determine its weight, or mass-to-charge ratio, which in turn helps to identify the specific ion. Since LC/TOF-MS collects full spectrum information on samples, the mass spectrometer can examine the data for non-targeted (or unknowns) as well as targeted information that is stored in a spectra database. Using a standard sample preparation procedure like QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe), a LC/TOF mass spectrometer like the PerkinElmer AxION 2 TOF provides lab scientists with the ability to rapidly detect hundreds of commonly regulated pesticides in food at or below the regulatory limit of 10 ppb in concentration. These instruments can also quickly and automatically highlight those residual amounts of pesticides that are above the regulatory limit. LC/TOF technology is an example of how to detect residual amounts of neonicotoid pesticides in honey, which are now the most commonly used insecticide class in the world and are currently under investigation as a possible cause for bee colony collapse disorder.
LC/MS/MS. Liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS), or triple quadrupole system, is becoming the method of choice for the detection of multiple residual pesticides in food, nutraceuticals, and botanicals. LC/MS/MS systems have a unique detection mode called multiple reaction monitoring, which allows the first quadruple in the system to select the parent ion mass of the analyte before sending them to collision cell for fragmentation. Following this the second quadrupole is able to select daughter ion from those parent ions and send them to the detector for detection. The unique parent/daughter ions combination provides high specificity, selectivity, and sensitivity. Using systems such as the PerkinElmer Altus UPLC system coupled to a QSight 220 triple-quad mass spectrometer can allow lab scientists to identify and simultaneously quantify the trace residue of multiple pesticides in fruit faster than other GC technologies.
In addition, portable GC systems are available when the lab is needed onsite. For example, the 32-pound Torion T-9 GC/MS by PerkinElmer can provide rapid screening of chemicals in food safety applications.
When it comes to flexibility, speed, and accuracy in testing for residual pesticides in food to meet global regulatory requirements there is a wealth of chromatographic options to help make the next family dinner be as pesticide free as possible.
Qin is product manager for food solutions at PerkinElmer. Reach him at email@example.com.