3 May 1999: HORMONES - Abusive use and difficulties of controls of growth hormones increase risks

Abusive use and difficulties of controls of growth hormones increase risks

Abusive uses can include misplacement of approved implants, off-label uses of hormonal growth promoters, use of multiple implants simultaneously or within very short time intervals and the use of unapproved substances obtained on the black market. In detail, the report points to the following deficiencies :

• In the USA and Canada, approved hormonal growth promoters are freely available over the counter. They can be obtained without veterinary prescription and used without supervision by a veterinarian.
• Although regulations require that implantation be restricted to the animal´s ear, it cannot be excluded as examples prove that implantations or injections are also made elsewhere on the animal´s body.
• When implantation sites enter the food chain, the exposure and risk to humans increases. For example, a single implantation site can contaminate a batch of 4000 glasses of baby food so much that consuming even one glass would result in a dose to a baby of up to 33 times of what would be acceptable consumption for one day.
• Although hormonal growth promoters are not approved for use in veal calves, recent Canadian surveys showed residues of the synthetic hormone trenbolone in 32-40 % of liver samples from veal calves.
• Although melengestrol acetate is approved for use in heifers only, it has been proven to be applied in US male animals, too.
• In the USA and Canada, repeated treatment of animals with hormones is common.
• Unapproved hormonal substances are available on the black market.
• Neither the US nor the Canadian meat inspection regulations provide for regular checks of animal carcasses for misplaced implants, even though in 1986 the US inspection service reported widespread misuse of hormone implants.
• Within the framework of the US National Residue Program no residue examinations have ever been performed for the three hormones 17ß-estradiol, progesterone and testosterone or for trenbolone acetate. No residue tests have been performed for zeranol since 1989 and for melengestrol acetate since 1990. No residue testing has ever been performed as part of that program for illegal hormonal growth promoters other than DES.
• The lack or insufficiency of residue control programmes and /or their insufficient enforcement increase the probability of not detecting misplaced implants, off-label uses and the use of black-market substances.
• The lack of adequate residue control programs increases the probablitity of human exposure and risk. A recent study of allegedly «non-hormone-treated bovine meat » found 12 % of 258 meat and liver samples positive for trenbolone, melengestrol acetate and/or zeranol.
• Each of the documented scenarios is cumulative and the effects may be additive. For example, if multiple implants were administered to veal calves, together with intramuscular injections of « cocktails » of black-market substances, then the model calculations for exposure from contaminated baby food provided above would be exceeded.

Concerning the risks of misuse, the Scientific Committee on Veterinary Measures relating to Public Health had concluded that higher doses and more frequent applications will obviously result in higher residue concentrations in tissues of treated animals. Concerns have been expressed for the potential risk of extremely high residue levels if implants are misplaced, which includes the possibility that the total content of an implant will be present in a portion of minced meat or in a batch of meat products. These extreme concentrations might exert acute hormonal effects and increase the likelihood that genotoxic metabolites are formed.