Chemical Food Contaminants (Hormones & Antibiotics) – V

Hormones and Antibiotics

It is not possible to give an unequivocal assurance that the use, antibiotics and hormones in food production will not result in residues that may be hazardous for some individuals. If the directions for the 'safe' use these substances are not followed (for example, if too much is used or it is applied at the wrong time) then there is the potential for hazardous residues to enter the food chain. The potential effects of these substances on health are one of the greatest concerns to consumers.

Before looking at these substances individually, let us look at some of the factors that determine whether a particular food component - natural, deliberately added or contaminant - is likely to be harmful. The most important factor is the amount of the component that we consume which is determined by both the amount of a particular food eat and the level in the food. Even if the level of a particular contaminant is low, it could still be hazardous if you eat a lot of the food or foods in which it is present. Just as some people may be sensitive to particular foods, food ingredients or food additives, some may be sensitive to residues of pesticides, antibiotics and hormones in food. There is no evidence to suggest that this is a common phenomenon and it is certainly far less common than reactions to foods such as milk, eggs, fish, and shellfish and nuts. 

International Aspects

The United States and Canada contested the prohibition of the use of hormones as growth promoters in food producing animals, and in 1997 a panel of the World Trade Organization (WTO) ruled that the EU measure was not in line with the Agreement on the Application of Sanitary and Phytosanitary Measures (SPS). The EU appealed against this ruling and, in 1998, the WTO Appellate Body reversed most of the findings of the panel. The WTO Appellate Body only upheld the finding that prohibition of imports of meat from hormone-treated animals to the EU did not comply with the requirement that such a measure should be based on a relevant assessment of the risks to human health. In reaction to these findings, the EU mandated a new assessment of the risks to human health from hormone residues in bovine meat and meat products treated with six hormones used for growth promotion. Subsequently the EU amended Directive 96/22/EC by adoption of Directive 2003/74/EC and thus implemented its international obligations in the context of the World Trade Organization.

Antibiotics

This is a group of drugs approved for use in animal led to stimulate growth and improve feed efficiency (so that less feed is required for growth) and also to reduce infection and stock loss. Higher levels are sometimes used (on prescription) for the prevention or treatment of infection. Following their use, a suitable lag time is necessary to prevent food contamination where use of antibiotics in food production poses certain public health risks, including the emergence of antibiotic-resistant microorganisms and possible sensitive reactions in certain people. Resistance to antibiotics is not harmful in itself, but it may create health hazard if humans become infected with a strain microorganism that cannot be controlled by available antibiotics. The majority of allergic reactions have occurred with penicillin. The treatment of bovine mastitis with large doses of penicillin requires a withholding period before the residues in milk are reduced to acceptable levels. If the treatment procedure is not followed the residues may cause allergic reactions in sensitive people. It is possible that oral exposure to penicillin in milk may also cause some individuals to become sensitized. 

Although antibiotic residues in foods can have a detrimental effect on the processing of cultured products such as cheese, and are important in terms of consumer confidence, the public health significance of residue concentrations of some of these compounds in foods from animals appears to be low, based on substantial scientific assessment. Most of the antibiotic drugs currently used in animal agriculture are relatively non-toxic, even at high concentrations, but there are a few antibiotics which pose a small but significant threat to public health when present in sufficiently high concentrations in foods. Among these is chloramphenicol, which has been associated (in a non-dose related manner) with aplastic anaemia due to bone marrow depression in a small proportion of human patients to whom

the drug was administered for therapeutic purposes. Some of the patients who survive the bone marrow depression have developed leukaemia, which creates concerns about possible carcinogenicity. Based on animal bioassay data, nitrofurans and some anti-parasitic drugs, such as dimetridazole, also raise some concern of carcinogenicity. Other antibiotics have been associated with allergic reactions of varying severity in people. An estimated four to ten allergic reactions occur per 100,000 courses of penicillin treatment administered directly to people, but actual incidents of allergic reaction to penicillin residues in foods are few and poorly documented. Although sulfonamides and tetracyclines administered to people at therapeutic concentrations may have toxic and allergic consequences, there is little evidence that these occur at the concentrations at which residues are encountered in foods. Based on experimental evidence, however, there is concern that residue concentrations of antibiotics have the potential to encourage the development of antibiotic resistance in the microbial flora of people eating contaminated foods.

Hormones

Hormones can be used to accelerate the growth rate of animals so that they can reach market earlier. The most effective growth promoters are natural sex hormones or substances which imitate the action of the natural hormones. If hormones are used appropriately, the residues in food should be very low or undetectable and not result in a significant hormonal effect. In some countries, abuses in the use of these substances have occurred and hormonal treatment has left high residues in poultry, veal and eggs which have resulted in breast enlargement, premature cessation of pubertal development and ovarian cysts in children. In view of these potential health hazards it is important that foods are monitored for hormone use and residue levels. This does not appear to be done on a suitable scale in Australia.

The use of hormones for growth promotion in meat animals, or for enhancement of milk production in dairy animals remains a very controversial issue. Two items continue to be debated, where the effects of residues of these chemicals on human health and the economic, social and political implications of banning the use of these compounds in agriculture. At present, these compounds are used legally to a varying degree in many countries; thus European Union has considered a repeal of the ban on these compounds which was instituted a few years ago as a result of public and political pressure. Historically, some of the public health concern over these compounds emerged from the observed association of DES treatment of women with reproductive problems and cancer in some female offspring. Secondly, there have been a few (generally unconvincing) reports in the literature which link precocious sexual development in children and possible exposure to foods contaminated with hormonal residues in foods.

However, in the context of food safety, the hormonal substances used in food animals can be usefully considered as belonging to two main groups: those which occur naturally in animals (and therefore also in humans) and those which are synthetic compounds and which do not occur naturally in animals (so-called steroidal and non-steroidal xenobiotics). Among the naturally-occurring compounds are testosterone, progesterone, oestrogen and somatotropin: the fact that BST in particular has been genetically engineered for commercial purposes (recombinant bovine somatotropin [rBSTJ), with minor structural differences from the natural hormone, should be noted. As a general rule for risk assessment, the presence of residues of the active hormone in foods should be no cause for concern with regard to public safety if the concentrations of the exogenous, naturally-occurring hormone in edible tissues from treated animals do not differ significantly from those in untreated animals. This can be justified although some of these compounds (i.e., the sex steroids) can act as tumor promoters.