It has emerged in recent hours that 23 top Chinese swimmers tested positive for the same powerful banned substance seven months before the Tokyo 2021 Olympic Games, but continued to compete. The World Anti-Doping Agency (WADA) was quick to respond with a public note. 

"WADA was notified in June 2021 of the decision by the China Anti-Doping Agency (CHINADA) to accept that the swimmers had tested positive for TMZ in early 2021 after being inadvertently exposed to the substance through contamination. As it always does, WADA carefully reviewed the decision and in this case requested the full case file," it started. 

"As part of its review, WADA gathered additional, unpublished scientific information on TMZ and consulted with independent scientific experts to test the contamination theory and also whether low doses of TMZ could have benefited the athletes during a swimming competition event," the organisation said in a statement," it continued.

"During this review process, scientists and external legal counsel thoroughly tested the contamination theory presented by CHINADA. It was not possible for WADA scientists or investigators to conduct their research on the ground in China due to the extreme restrictions imposed by a COVID-related lockdown," the WADA pointed out. 

The organisation asseured that "it could not rule out the possibility that contamination was the source of TMZ and that it was consistent with the analytical data in the file and that, given the specific circumstances of the alleged contamination, the athletes were not at fault or negligent. As such, and based on the advice of external counsel, WADA considered that an appeal was not warranted." 

WADA Senior Director, Science and Medicine, Olivier Rabin, said: "WADA's scientific department thoroughly reviewed this case in June and July 2021. We even requested new pharmacokinetic and metabolism information on TMZ from the manufacturer and tested several hypotheses, including low-dose TMZ doping strategies, to assess the plausibility of the contamination scenario presented to WADA. Ultimately, we concluded that there was no concrete basis to question the alleged contamination." 

"Indeed, the contamination scenario was further supported by the combination of the consistently low concentrations of TMZ and the absence of a doping pattern with several athletes submitting multiple samples collected over the course of several days that fluctuated between negative and positive (and vice versa). In full transparency, we have communicated the conclusions of our scientific review to internal and external investigators, including the International Testing Agency," he continued.

The statement setressed that "in 2022, the International Testing Agency raised issues with WADA regarding a possible misreporting of the TMZ samples. This was independently reviewed by WADA's Intelligence and Investigations Department, which concluded that proper procedures had been followed and that there was no evidence of wrongdoing. The United States Anti-Doping Agency (USADA) then contacted WADA by email in April 2023 regarding the TMZ cases. It informed WADA that it had received a tip-off from an unspecified source that the TMZ positive cases had been concealed."

The organisation said that the information "was clearly inaccurate as the TMZ positive cases had been reported and adjudicated by CHINADA and thoroughly reviewed by WADA and World Aquatics almost two years earlier. USADA had also contacted WADA in 2020 (prior to the TMZ positives) regarding allegations (again from an unspecified source) of doping cover-ups within Chinese swimming." 

"These allegations were (again) completely unsubstantiated and WADA advised that the threshold for opening an investigation had not been met. However, WADA offered to reassess the situation if USADA provided any evidence at all, which it did not. WADA I&I also offered to interview the USADA source but this offer was not taken up," the WADA continued.

WADA Director of Intelligence and Investigations, Gunter Younger, said: "At every stage, WADA I&I followed all due process and diligently investigated all leads and lines of enquiry in this matter. The information provided to us by USADA and others was reviewed on each time in accordance with our procedures and assessed according to the criteria set out in our Confidential Source Policy." 

"The data held by us clearly showed that there was no attempt to hide the positive tests as they were reported by the Chinese authorities in the usual manner. Therefore, based on the information available and in the absence of any credible evidence, the threshold for WADA I&I to open an investigation was not met," he concluded.

The organisation concluded by saying that "as a result of the misleading information published this week, including on social media, WADA reserves the right to take legal action as appropriate."