High levels of absorbed cocaine have been found in South Wales’ wastewater, according to a new study.

The BBC reports the largest consumption was found to have peaked during rugby internationals in Cardiff in 2021, when Wales faced South Africa, which found 8.54 milligrams of the illegal drug per day, per 1,000 people.

By comparison, the two other sites recorded levels of just 3.88 milligrams and 1.97 milligrams per day, per 1,000 people.

A spokesperson for Public Health Wales said the study coincides with the increasing cocaine use they have seen in recent years and highlights the benefits of identifying drug use trends.

The study set out to understand the levels of use of new psychoactive substances in South Wales and was carried out by Bournemouth University’s Analytic Research Group.

But the main substance detected in wastewater samples was benzoylecgonine, a compound that is produced when the body breaks down cocaine.

The first study of its kind in Wales, it looked at samples before and after being purified, from Friday to Monday every week, over a two month period.

PhD student Bethan Davies, who led the study, said the Wales v South Africa rugby weekend seen a significant increase of footfall, where absorbed cocaine was at its highest across the study.

Despite the public health concern, she said the development could help in addressing drug monitoring and improving treatment.

She said “By knowing what is popular within certain communities, we can tailor how we test for substances in different areas and avoid spending time and resources testing for drugs that are not around.”

On average, 73% of benzoylecgonine was removed during treatment, meaning traces remained in the water that went back into the region.

But Welsh Water confirmed that the post-treated wastewater is not forwardly used for drinking, but for non-consumption.

In a statement, Welsh Water said “Our drinking water is provided from a completely separate system and is highly regulated so the water we provide is of the highest quality.”

Bethan Davies also confirmed that if the wastewater was consumed post-treatment, the levels should not cause any issues to public health.

Dr Giri Shankar, Director of Health Protection for Public Health Wales, said the study highlights the benefits of identifying drug use trends.

He said “The findings are consistent with our own research, which shows a trend of increasing cocaine use in recent years.

“We have monitored an increase in the number of assessments for cocaine, including crack, by substance misuse services in Wales.

“The number of deaths from drug-related causes remains unacceptably high in Wales.”