There are calls to overhaul drinking water guidelines after a troubling new study suggested a weedkiller found in Australia’s waterways could be harming male fertility by reducing sperm counts.
In mice, a dose of atrazine at what the government says is a ‘safe level’ appears to cut sperm counts, the new research reveals. Low levels of atrazine have been shown to turn male frogs into hermaphrodites.
The researchers believe the chemical could be linked to the more-than-50 per cent decline in human sperm count seen over the last 50 years.
Multiple government investigations have determined that low levels of atrazine do not pose a risk to human health based on long-term studies that showed exposed animals were not any more likely to develop human-relevant cancers, nor more likely to have reproductive problems.
That is the wrong test, says Dr Andrew Pask, the University of Melbourne scientist who led the research.
“These tests are missing atrazine’s subtle effects on fertility.
“We showed this chemical massively reduced the fertility of the males – and they became obese. This chemical is very damaging, even at this low concentration – which is not uncommon in Australia’s waterways.”
Government tests looked at high doses of atrazine. But Dr Pask’s work has shown it is extremely low doses that seem to have the greatest effect on fertility.
In the study, published this week in Reproduction, Fertility and Development, Dr Pask’s lab gave mice atrazine-spiked water (at the levels considered safe by regulators) for eight weeks.
By the end of the experiment, those mice had significantly reduced sperm numbers, and their remaining sperm was of lower quality. Atrazine appeared to convert testosterone to estrogen, effectively feminising the male mice, the research found.
“The observations are new, but they are not necessarily surprising,” says Professor Stuart Khan, who sits on the Water Quality Advisory Committee that sets Australian drinking water guidelines but spoke in his role as a scientist at the University of NSW. He was not involved in the study.
“I’m very open to the possibility that this work might support the need to reduce drinking water guideline concentrations [of atrazine] to ensure a safe level of exposure.”
Both WaterNSW and Melbourne Water monitor atrazine in drinking water catchments. Both say detected levels are hundreds of times below safe drinking water levels.
The EU banned atrazine in 2004 over groundwater contamination fears, while the US has installed safe drinking water limits much lower than Australia’s. Our farmers still spray about 3000 tonnes a year onto crops, and it is one of the most-commonly detected weedkillers in Australian waterways.
“You can find atrazine in most waterways in Australia. It will be in the drinking water too,” says Dr Jon Brodie, a water pollution researcher at James Cook University who led some of those detection studies.
“But it will never be banned in Australia, no matter what scientists find – because we have got the weakest pesticide regulator in the whole developed world. They are industry-captured.”
In 2008 that regulator, the Australian Pesticides and Veterinary Medicines Authority, released its atrazine investigation that concluded the herbicide did not pose human health risks.
But the report noted there was some emerging evidence atrazine effected fertility by ‘feminising’ animals – converting the male sex hormone testosterone into estrogen during development. However, at the time, the Authority concluded there were not enough studies on the effect.
Importantly, studies on animals often do not translate to results in humans, and there is no human data on atrazine’s effect on fertility.
But Dr Pask believes a large-scale human fertility crisis is being caused by exposure to chemicals such as atrazine. Known as ‘endocrine disrupters’, these chemicals – which include BPA and other plastics – appear to mimic human sex hormones, disrupting fertility.
He points to a large study showing fertility had declined by more than 50 per cent since 1972 in the western world. Australian studies have shown penis birth defects have almost doubled since 1980.
The APVMA has been contacted for comment.