THERE are plenty of reasons why our use of plastic is bad — but this one is aimed at the blokes.

Expanding on previous studies that have shown the stuff in plastic can cause damage to penises and make them smaller, two Aussie scientists are furthering the work and say more boys are even being born with genital defects because of it.

University of Melbourne researchers Associate Professor Andrew Pask and Dr Mark Green say they have shown penis birth defects have doubled in Australia because of plastic.

To prove that, they studied human data and animals exposed to the chemicals to see whether they have the defect called hypospadia, a condition that means the opening of the penis is on the underside rather than the tip and causes functionality problems.

The pair have identified several chemicals that are known to cause damage to humans, that we either consume through food contamination or in our water.

Dr Pask and Dr Green aren’t the first to do so. In 2014 a study led by Sweden’s Karlstad University showed the effects of phthalates, a common component of many products, on young males.

The researchers showed a significant shortening of the distance between the anus and the penis.

In 2015 a small French study found a “strong” link between exposure to endocrine-disrupting chemicals during pregnancy and hypospadia.

And an Italian study in 2010 did the same.

Zero waste promoter Bea Johnson even references the terrifying claim in her talks, giving the men in the room just another reason not to use plastic on her recent Australian tour.

Dr Pask and Dr Green believe they are Australia’s only scientists studying the chemicals’ effect on male reproduction.

Those chemicals include BPA and phthalates, parabens used in toothpastes and beauty products and atrazine in herbicide.

“Exposure to these chemicals, this is the No. 1 reproductive issue for men,” Dr Pask told The Sydney Morning Herald.

“No one likes to talk about this. Often parents don’t even like to tell their kids they had it — it gets surgically repaired but often the surgeries don’t work very well.

“When it’s doubling, it cannot be genetic defects — it takes years for that to spread through a population. So we know it has to be environmental in origin.”

Dr Pask said they had laced a pregnant mouses’s water with atrazine to prove it gives the baby hypospadia. He said the damage can get worse over generations in animals.

The link to humans is that we have been exposed to these chemicals over two generations since the 1950s.

While the evidence in animals in clear, experts say we still cannot be categorically sure about the damage human exposure can do.

BPA can leach from containers into food, particularly foods that babies and small children eat.

The World Health Organisation has launched a review after microplastics were found in 90 per cent of bottled water.

Analysis of 259 bottles from 19 locations in nine countries across 11 different brands found an average of 325 plastic particles for every litre of water being sold.

This week an episode of ABC’s War on Waste tested popular water bottles and found tap water often came out better.