Since decades clenbuterol is applied illegally in cows and pigs to increase muscle growth and thus to achieve economical benefits from cultivating more meat per animal. China as well as some other countries in Asia are typical countries with a high incidence of clenbuterol application and weak policies to prevent that. Because residues of clenbuterol can persist in meat, athletes are at risk for being positive unintentionally for traces of clenbuterol. As anti-doping laboratories can detect low traces of clenbuterol, the WADA was forced already in 2011 to clarify its anti-doping policy: WADA states, that “It is possible that under certain circumstances the presence of a low level of clenbuterol in an athlete sample can be the result of food contamination. However, each case is different and all elements need to be taken into account. Under the World Anti-Doping Code, result management of cases foresees the opportunity for an athlete to explain how a prohibited substance entered his/her body.
Although the WADA policy can be justified, it is an extreme challenge for athletes with positive result for clenbuterol to prove that the source of clenbuterol was meat and not intentional abuse. It is remarkable that in the WADA statistics the number of clenbuterol positives in the last decade is increasing in time, namely from 0.2‰ in 2004 to 1‰ in 2017. This increase is very likely to represent ingestion of contaminated meat, rather than an increase of active abuse of clenbuterol by athletes. After all, introducing new analytical technologies in routine anti-doping analysis around 2010 has expanded the detection possibilities of clenbuterol.
Moreover, it should be underlined that the association of being positive for clenbuterol after the ingestion of meat from cows and pigs is incomplete. In Asia the image of illegal use of clenbuterol is focussed normally on breeding cattle and poultry. However, because of the concept of integrated aquaculture in Asia, fish is also involved. Integrated aquaculture is a system typically practiced by Asian small-scale farms. They keep livestock in units located either above or near a fishpond, allowing faeces and urine as well as excess feed of cattle directly into the pond. These nutrients act as fertilizer and facilitate the growth of various kinds of algae serving as fish feed. Subsequently, if excessive feed and faecal wastes from the livestock contain clenbuterol, fish will be contaminated also. This scenario and the possible risk is illustrated by findings of clenbuterol in meat and livers versus that in wastewater from livestock farms and surface water in Malaysia. While the illegal use of clenbuterol in livestock in Malaysia is widespread, that wastewater of farms is contaminated also.
Because of the contamination of fishponds, the issue of contaminated meat is not limited to cattle and poultry, but also includes that of fish. This is of special importance, as warnings of anti-doping authorities to athletes to consume meat, is stimulating athletes to look for alternative sources of animal proteins. By misconception meat might stand for meat of cattle and poultry and not for that of fish. Therefore and unfortunately, fish might be considered as a safe source of meat free of clenbuterol, which is incorrect. Because China and other Asian countries export their fish all over the world, one does not need to be in China and to be at risk for being positive for clenbuterol.
– WADA 2011. WADA statement on clenbuterol. 15 June 2011 https://www.wada-ama.org/en/media/news/2011-06/wada-statement-on-clenbuterol
– WADA 2017. WADA statement on ARD documentary. 2 April 2017 https://www.wada-ama.org/en/media/news/2017-04/wada-statement-on-ard-documentary accessed 28 December 2018.
– WADA 2019. What is the status of clenbuterol? https://www.wada-ama.org/en/questions-answers/prohibited-list-qa#item-386 accessed 28 December 2018.
– Li K, Liu L, Zhan J, Scippo ML, Hvidtfeldt K, Liu Y, Dalsgaard A. Sources and fate of antimicrobials in integrated fish-pig and non-integrated tilapia farms. Sci Total Environ. 2017;595:393-9.