Multiple chemical contaminants in foods

Over the past decade, the presence of chemical contaminants in foods has probably had a greater impact on the global food trade than any other food-related issue.The reasons for the continued attention directed towards chemical contaminants are complex and associated with a number of separate, yet interrelated factors.

There are a huge number of chemical classes that can end up in a wide variety of food commodities with numerous reasons for this type of contamination. These include heavy metal contamination resulting from industrial waste and pesticide accumulation in food due to the widespread use of chemicals in agriculture. The multitude of veterinary medicines and growth-promoting compounds used in virtually every class of livestock production can also result in the contamination of animal-derived products with drug residues.

In addition to man-made sources of contamination, chemicals derived from natural sources may also be present in food products, for example, mycotoxins from moulds which accumulate in cereals and nuts or phycotoxins from algae present in shellfish. Collectively, these contaminants can number in the thousands and if their breakdown products, i.e. metabolites, are also taken into consideration, the number increases by a factor of three or four.

Risk to the consumer

The potentially harmful effects of these chemicals on the consumer merits attention.Although toxicological data has been produced which examines a wide range of these compounds individually, the effects of food containing ‘chemical cocktails’ on human health is far from being fully understood. It is probably fair to say that this lack of knowledge is due to a lack of technologies capable of accurately predicting the medium- to long-term effects of the consumption of chemical cocktails.Although there are those who believe that the chemicals are present at such low concentrations that they do not constitute a significant risk overall, no consensus has been reached. Others are of the opinion that the adverse effects of contaminants on the consumer have been underestimated and play a role, albeit secondary, in many disease states.

Contaminants and trade

The complexities associated with the presence of chemicals in foods can be fully appreciated by adding yet another factor to the ‘chemical contaminant equation’, i.e. regulation by law. The presence or absence of chemicals in foods can determine whether products may be exported or imported under the national and international laws related to MRLs or safe limits.

Measuring contaminants

On the technology front, the most important change with regard to monitoring chemical contaminants in foods has been the increase in the sensitivity of the monitoring procedures. In many cases minute traces (less than one part per billion) of a single contaminant can be detected. This development has not been without controversy. There are those who claim that having this degree of analytical sensitivity means that food is safer, as fewer products enter the food chain with any degree of contamination. The alternate view is that the concentrations being detected are so low that the data generated is meaningless from a food safety perspective. This results in food being destroyed unnecessarily or trade restrictions being imposed for no logical reason. No doubt this argument will continue to rage between regulators and producers.

Within the European Union, the need to convince consumers that the food they eat is safe and wholesome has been a major driving force for research. The European Commission (EC) has funded a great deal of research in the area of food safety and quality in recent years and this, if anything, is likely to increase over the next decade.

The largest research project funded by the EC in the area of chemical contaminants in foods is BioCop: ‘New Technologies to Screen Multiple Contaminants in Foods’. Widely believed to be the largest project of its kind in the world, this is a five year research project with 33 participating partner organisations co-ordinated from Queen’s University in Belfast. The project has been constructed to supply regulators, consumers and industry with long-term solutions to the complex problems associated with chemical contaminant monitoring. The ultimate goals of the project are:

• To determine which of the emerging life science technologies are most suited to delivering high quality, cost effective monitoring for multiple types of chemical contaminants that might be present in foods
• The training of scientists within the project and from external laboratories to use the newly developed analytical tools in the most effective manner
• The widespread dissemination of project information to audiences ranging from scientists to consumers and regulators
• To eventually bring the new tests developed to the market place by including the wide range of commercial partners included in the project

Within BioCop a range of new approaches, such as transcriptomics, proteomics and biosensor detection will be utilised. The majority of the new approaches are based on measuring the effect of the contaminants, rather than relying on the measurement of single target compound concentrations. The ‘biomarker and fingerprinting’ concept is key to this strategy.

Two examples of how Biocop technology platforms are being developed to deal with multiple contaminant issues are described here.

Transcriptomics

A high-throughput system for the screening of contaminants in food samples through the exploitation of contaminantspecific transcriptional profiles will be developed.What does this mean? When subjected to toxic stimuli, cells react by changing their protein expression patterns. It is known that different kinds of cellular stress generate distinct ‘alarm’ responses. Specific transcriptional ‘alarm’ responses to phytoestrogens (oestrogen-like compounds of plant origin), mycotoxins (toxic metabolites produced by fungi) and organochlorine pesticides, will be identified. Once these specific patterns have been identified, a novel high-throughput platform will be developed by the German company Clondiag GmbH to allow low-cost screening of all these compounds.

Biosensors

From being a technology thought of as only suitable for academic research, biosensors are increasingly finding their way into many routine testing applications within the food industry.With regard to food contaminant analysis, the Swedish company Biacore is now widely recognised as a supplier of leading edge technology for regulatory and industrial-testing laboratories.

Within BioCop, working in very close association with leading proteomic research groups, the company is developing a completely new instrument dedicated to simultaneously quantifying multiple biomarkers that have been identified as diagnostic for the effects of illegal growth promoting drugs administered to cattle. This effect-orientated approach has a clear advantage over existing technologies in terms of throughput and will have the powerful ability to detect newly developed designer steroids and hormone cocktails.

Samples from animals will be injected directly into the instrument and biomarkers captured using specific receptors developed within BioCop. Results from this biomarker assay will define the probability that a certain animal has been illegally treated with growth promoters. It is believed that each type of growth promoter will have a unique influence on the concentrations of the various biomarkers and will therefore generate ‘protein fingerprints’ capable of identifying the growth promoter to which the animal was exposed.

These are only two examples of the ambitious research projects that are underway within BioCop, but there are many more. Other examples include the development of unique binding proteins for many contaminants, of novel sample extraction procedures and portable sensing devices for contaminants.

More information about the scope and progress of the project can be obtained at www.Biocop.org with demonstrations of the technologies developed and how they can be used to help deliver safer food for consumers.