FRI BRIEFINGS Human Safety of Hormone Implants Used to Promote Growth in Cattle A Review of the Scientific Literature Ellin Doyle, Ph.D. Food Research Institute, University of Wisconsin Madison, WI 53706 TABLE OF CONTENTS Introduction and Historical Background ........................................... 2 Hormone Metabolism and Toxicity in Humans ................................ 4 Toxicity Studies in Animals and Cell Cultures ................................. 6 Genotoxicity Assays ........................................................ 6 Carcinogenicity Assays .................................................... 8 Other Toxicity Tests/Issues ............................................. 8 Hormone Concentrations in Cattle Tissues ....................................... 9 Estradiol ......................................................................... 10 Progesterone................................................................... 11 Testosterone ................................................................... 11 Trenbolone ..................................................................... 11 Zeranol ........................................................................... 12 Assays for Determination of Hormone Levels................................. 12 Hormone Concentrations in Other Foods ........................................ 14 References ....................................................................................... 15 Acknowledgments ........................................................................... 24 Food Research Institute, July 2000 http://fri.wisc.edu/docs/pdf/hormone.pdf 2 FRI BRIEFINGS: Human Safety of Hormone Implants for Cattle Growth Promotion INTRODUCTION AND HISTORICAL and inserted in cattle as recommended would not BACKGROUND result in residue levels in meat that would adversely affect human health (99, 117, 121, 158, 196, 209). Hormone implants containing estradiol benzoate/ Two dissenting reviews (2, 184) expressed concern progesterone were first approved in 1956 by the about the safety of these implants. Another recent U.S. Food and Drug Administration (FDA) for in- review (105) considered the implications of hormone creasing growth, feed efficiency, and carcass lean- pellets that were not properly implanted or discarded ness of cattle. Later, other implants containing at slaughter. testosterone, zeranol, trenbolone acetate, and combi- The FDA has established maximum safe tissue nations of these hormones were developed and ap- residue levels for trenbolone (19) and zeranol (17) proved for use in cattle by the FDA. as listed below:* Currently, five hormones (progesterone, testos- terone, estradiol-17β, zeranol, and trenbolone acetate) Muscle Liver Kidney Fat Hormone (µg/kg) are approved for implants in cattle in the U.S.A. But these implants have been officially prohibited Trenbolone 50 100 150 200 Zeranol 150 300 450 600 in Europe since 1989. Hormone implants are widely used in the U.S.A., Australia, and Canada. Accord- µg/kg = ppb (parts per billion) ing to a review by Preston (158), approximately 30 *Please refer to note (*) on metric units at the end of countries have approved one or more of these the text if these units are unfamiliar. implants for enhancing the growth of cattle. Use of For the naturally occurring hormones estradiol these implants in cattle according to recommended (20), progesterone (15), and testosterone (16), FDA procedures was declared safe by the following has set the following allowable incremental increases groups: in hormone levels above those normally present: ◆ FDA, which approved 11 formulations of implants between 1956 and 1996 (15–21, 158) Muscle Liver Kidney Fat Hormone (µg/kg) ◆ EEC Scientific Working Group on Anabolic Agents, chaired by Dr. G. E. Lamming in 1987 Estradiol 0.12 0.48 0.36 0.24 Progesterone 3 12 9 6 (185) Testosterone 0.64 2.6 1.9 1.3 ◆ Codex Committee on Residues of Veterinary µg/kg = ppb (parts per billion) Drugs in Foods, in 1987 (24) ◆ European Agriculture Commission Scientific JECFA has set lower maximum residue limits Conference on Growth Promotion in Meat for both zeranol (98) and trenbolone (97) at 2 µg/kg Production, in 1995 (79, 158) in meat and 10 µg/kg in liver. Acceptable residue ◆ FAO/WHO (Food and Agriculture Organization/ levels for estradiol, progesterone, and testosterone in World Health Organization) Joint Expert meat have not been recommended by JECFA be- Committee on Food Additives (JECFA), 1981, cause this committee concluded that residues from 1983, 1988, 1999 (94–103) use according to good husbandry practice are un- ◆ Sub-Group of the Veterinary Products likely to pose a hazard to human health (99, 158). Committee from the Ministry of Agriculture, Acceptable daily intake (ADI) maxima of estradiol, Fisheries, and Food (UK), 1999 (196). progesterone, and testosterone were established by JECFA at 0.05, 30, and 2 µg/kg body weight (bw), Hormone implants in cattle have been the sub- respectively, based on reported no- or lowest- ject of eight significant reviews in the past five years. observed-effect levels in humans of 5 µg estradiol/kg All except two of these reviews concluded that im- body weight, 3.3 mg progesterone/kg bw, and 1.7 mg plants containing the approved doses of hormones testosterone/kg bw (99). ADIs for zeranol and Food Research Institute, July 2000 http://fri.wisc.edu/docs/pdf/hormone.pdf FRI BRIEFINGS: Human Safety of Hormone Implants for Cattle Growth Promotion 3 trenbolone acetate were set at 0.5 and 0.02 µg/kg bw which “covers cases where scientific evidence is based on feeding experiments with cynomolgus insufficient, inconclusive, or uncertain and prelimi- monkeys (98) and pigs (103). nary scientific evaluation indicates that there are Safety of hormonal implants has been ques- reasonable grounds for concern ...” (3). The con- tioned on the basis that residues from these implants cerns expressed by the Committee members include: in beef may significantly increase exposure of ◆ Sensitivity of hormone assays. They humans, particularly children, to estrogens and other contend that the routinely used radioimmuno- hormones which may adversely affect health. Estro- assay is not sensitive enough to accurately gens are naturally present in all mammals, with higher measure low hormone levels in blood of concentrations in females during the reproductive children and perhaps in some meat samples. phase of their lives. According to evaluations by the Rather they propose that the very low International Agency for Research on Cancer (IARC; plasma hormone concentrations measured in 215), there is currently sufficient evidence for the children by the recombinant cell yeast carcinogenicity of estradiol and limited evidence for bioassay (109) are more accurate. the carcinogenicity of testosterone to humans. Ex- ◆ Effects of low concentrations of hormones. periments with some of the other compounds used in They argue that even though excess exposure implants have shown that, under certain conditions, to hormones in beef from implanted cattle they may cause adverse effects in experimental ani- may amount to as little as 1 to several mals. Although some recent data indicate that estra- hundred nanograms per person, pre- β diol-17 has genotoxic potential, JECFA scientists adolescent boys and girls and the fetus pointed out that there are no data demonstrating that in utero may be very sensitive to slight concentrations below the no-hormonal-effect level increases in hormone levels. (NHEL) cause adverse effects in animals or humans ◆ Irrelevance of NHEL (no-hormonal-effect (99). level). They point out that some recent data Whether residues of hormone implants in beef indicate that estradiol is genotoxic and constitute a health risk remains a controversial issue. therefore may have carcinogenic effects at The 1999 JECFA analysis (99) estimated that a concentrations below the NHEL. person consuming 500 g (about 1.1 lb) of meat from implanted cattle would consume an extra 30–50 ng In response, the 1999 review by the UK’s Sub- estradiol per day. This calculation utilized the highest Group of the Veterinary Products Committee (196) residue levels reported for implanted beef and consid- critically evaluated genotoxicity studies of estradiol ered “meat” as a mixture of 300 g muscle, 100 g liver, and concluded that “None of the publications (re- 50 g kidney, and 50 g fat. (Estradiol levels are higher search papers) reviewed above provide any substan- in organ meats than in muscle.) This additional 50 ng tive evidence that oestradiol is mutagenic/genotoxic.” estradiol consumed can be compared to the accept- The recombinant yeast cell bioassay was critically able daily intake of 50 ng/kg/day or 3000 ng/day for evaluated and this Committee was concerned that a 60-kg (132-lb) person. interfering substances in the crude extracts of serum In 1999, the European Commission also issued samples could have caused artificially low serum a report that discussed available data on hormone estradiol measurements. Further validation is re- implants and their potential toxicity and concluded quired for this assay. Although high concentrations that elevated levels of hormones in meat from im- of hormones can certainly disrupt normal metabolic planted cattle might present a hazard, particularly to processes, this Sub-group concluded that small in- children (184). Invoking the precautionary principle, creases in hormone intakes from implanted cattle the Committee decided that beef from implanted