The pilot study conducted by University of Otago-based biotechnology company Insitugen looked at the potential health impacts of using tampons made with synthetic fibres.
Insitugen chief scientist and physiology professor Alison Heather said the study, commissioned by period products company Organic Initiative, showed one of the four brands tested contained high amounts of oestrogen-mimicking chemicals, or xenoestrogens.
“Elevated xenoestrogen exposure can increase risks of many endocrine-related diseases, including endometriosis, polycystic ovarian syndrome and hormone-dependent cancers," she said.
It was a part of the wider societal problem of oestrogens from sources such as microplastic causing health issues.
"The tampon brand that has shown significant endocrine-disrupting activity is composed of plastics.
"The underlying concern is that we're getting oestrogen activity where we shouldn't have oestrogen activity."
The test results had surprised her, although they were in line with overseas studies.
She said she could not name the tampon brand that yielded the concerning results, but confirmed it was not Organic Initiative.
She understood further testing was being carried out elsewhere.
It was "very, very early stages" and more information was needed about the chemicals detected, their absorption and their impact.
However, she advised shoppers to look for period products that had been tested for endocrine-disrupting chemicals, something more and more companies were doing.
They should also avoid items such as plastic applicators until more was known.
"We're not trying to cause a scare for the public, but it's just a bit of an eye-opener, I think, for the regulatory authorities to start monitoring a little bit more."
More regulations were needed about the testing of products being sold to the public.
"Ultimately, that’s what I'd like to see around this."
