European opinion on hormonal growth promoters stands; effect on fish from feedlot run-off noted
A new report by the European Food Safety Authority (EFSA) indicates an association between large-scale beef cattle production using hormones, and undesirable effects in wild fish species living in rivers that are exposed to waste water originating from these farms.
EFSA concluded a study on behalf of the European Commission (EC) into new scientific evidence that might have emerged since the last risk assessment in 2002 relating to the use of natural and synthetic growth promoting hormones (GPH) in cattle.
Growth promoting hormones are used legally to increase the weight gain of cattle in many countries, although they are not permitted in Europe because of concerns about possible health risks from residues in the meat and other edible parts of these animals.
The substances under consideration are the naturally occurring steroids, testosterone and progesterone, as well as the synthetic compounds trenbolone acetate, which has demonstrated affinity to androgen receptors, zeranol, which has a high affinity for oestrogen receptors, and melengestrol acetate, which resembles progestins.
The report references a 2004 study that shows evidence of sufficient levels of hormonally active compounds released into the water by beef feedlot operations in Nebraska, USA to produce adverse effects on aquatic ecosystems.
Other studies showed male fish (fathead minnow) de-masculinisation (lower testicular testosterone synthesis, altered head morphometrics, and smaller testis size) and female de-feminisation (decreased oestrogen:androgen ratio) in river water that contained effluents from cattle feedlots.
The androgenic activity of 17β-trenbolone in fathead minnow, lowering fish fecundity, reducing plasma steroid (testosterone and 17β-oestradiol) and vitellogenin concentrations had been described before and has also been reported in mosquito fish. In a recently developed fish-sexual-development test (FSDT), significant effects of trenbolone acetate at concentrations exceeding 193 ng/L were observed, shifting a zebra fish population towards a dominance of males and decreasing itellogenin levels significantly.
A separate study quoted identified metabolites of trenbolone acetate (17α- and 17β-trenbolone) in a study assessing water samples from a beef feedlot in Ohio known to use trenbolone acetate implants. The samples for this study were collected in 2002 and 2003 and were subjected (in addition to the chemical analyses) to a bioassay using CV-1 cell line (transiently co-transfected with human androgen receptor vector), which indicated an elevated level of androgenic activity.
The Panel noted that the understanding of the complex mechanisms of action of steroid hormones is still a matter of scientific research and new insights into the complex genomic and non-genomic regulatory mechanisms controlling hormonal homeostasis in different phases of life are still emerging.
At present, epidemiological data provide convincing evidence for an association between the amount of red meat consumed and certain forms of hormone-dependent cancers. Whether hormone residues in meat contribute to this risk is currently unknown. Download full report (PDF)
