Widespread Plasticizer Clouds Doping Tests of Cyclists

News | Health

Cyclists get dinged for finding phthalates in their blood but argue that the chemicals are ubiquitous in all people these days

By Brett Israel ?| February 9, 2012?|

Image: Wikimedia Commons/Kallenovsky

In the race to catch drug cheats, sports officials are turning to more sophisticated tests. Since cheaters are rarely caught red-handed, scientists devised a plan to catch them with the packaging inside their bodies. But a plasticizer is so ubiquitous in people that it has clouded the results of these blood doping tests in the world of professional cycling.

Alberto Contador, a three-time Tour de France champion from Spain, was found guilty of doping Monday after he tested positive in 2010 for a performance-enhancing drug. A plasticizer, typically used to soften plastic bags or tubes, was also found in his system, which prompted allegations of an illegal blood transfusion.

Doping in the world of elite sports has grown so high-tech that officials began testing athletes like Contador not only for banned substances and illegal medical procedures, but also for trace evidence of cheating, such as the residues of IV bags.

Experts and Contador say that these chemical residues are so widespread that there is too much doubt about how they got into an athlete's body. But others say that spikes of these chemicals, at levels much higher than normal, are a red flag for doping. Due to the controversy, funding for the test to detect these chemicals was discontinued in November 2011.

In a preliminary test in 2010, Contador's urine sample showed a spike in plasticizers that are found in IV bags used to store blood, according to the ruling by an international sport arbitration panel.

The theory is that a cyclist with plasticizers in his urine was using the IV bags for blood doping illegally boosting one's red blood cell count to carry more oxygen to the lungs and muscles. But Contador's case has been controversial since the beginning, and he has vowed to appeal the ruling, saying that the widespread use of plasticizers in the environment has clouded the testing efforts of the sport's doping police.

The World Anti-Doping Agency funded research to develop a plasticizer test that would catch cheating cyclists, but so far it's not the smoking gun that many have hoped for. Plasticizers known as phthalates are used in everyday products, with possible toxic effects. The goal is to one day be able to prove that a plasticizer spike in a cyclist's urine was due to blood doping paraphernalia, and not, say, an accidental exposure from food.

The plasticizer in question is called bis(2-ethylhexyl)phthalate, or DEHP, which is "ubiquitous" in the environment, said Shanna Swan, a reproductive epidemiologist at the Mount Sinai School of Medicine in New York who has studied the effects of phthalates on infant boys.

"Ninety-eight percent of people in the U.S.A. have measurable levels," Swan said.

DEHP is only one of many phthalates in that are common in the environment. Phthalates can mimic estrogen or disrupt testosterone, and exposure of fetuses and infants is the major concern. In infant boys, prenatal exposure to dibutyl phthalate has been?linked to feminization?of the reproductive tract. In men, phthalate exposure has been?linked to sperm defects?and?altered thyroid hormones.

DEHP is the primary plasticizer in many medical supplies such as IV blood bags, which are about 40 percent DEHP. But it's also in food, and diet is the largest source of DEHP exposure, said Joe Braun, an epidemiologist at Harvard University. It apparently gets into food from use of some plastic food wraps and containers.

Since 2000, blood doping tests have been able to detect whenever blood from more than one person is present in a cyclist's sample (called a homologous blood transfusion). But these same tests cannot detect when a rider is doping with his own blood (autologous blood transfusion), so markers such as DEHP or its metabolites are needed to indicate foul play.

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