Scots scientists are taking part in a major new study to develop accurate tests for chemicals found in everything from cosmetics to food additives amid increasing alarm that they may be harming women’s fertility.

The five-year study at Aberdeen University will examine how chemicals known as endocrine disruptors affect a woman's reproductive health, and help to develop tests that are reliable enough to be used by regulatory bodies.

Endocrine disruptors are chemicals known to interfere with the body's hormone systems. They have been linked to tumours and birth defects, and there is mounting evidence that they reduce both male and female fertility - both of which appear to be in decline.

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Endocrine disrupting compounds are found in a range of substances including air fresheners, cosmetics, plastics, pesticides and food additives, but it is unclear at what dose they begin to cause problems.

Professor Paul Fowler, Director of the Institute of Medical Sciences at the University of Aberdeen, said: “We already know that endocrine disruptors can affect fertility, brain development and many other aspects of health.

"However, at the moment we do not have good tests to work out whether certain chemicals that require regulation, such food additives, plastic food containers, pesticides and biocides might disturb the endocrine system in people, especially women, thereby affecting their health and fertility.”

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The Aberdeen study is one of eight across Europe and the US under the umbrella of 'FREIA' (Female Reproductive Toxicity of Endocrine Disrupting Chemicals).

Others will examine links between endocrine disruptors and issues such as metabolism and thyroid function.

The €50 million (£44m) project as a whole will be overseen by Professor Majorie Van Duursen, at the Free University of Amsterdam.

Prof Van Duursen explains: “There is surprisingly limited knowledge on this issue. We will investigate how exposure to endocrine disruptors during different hormone-sensitive phases in a woman’s life, from during fetal development in the womb, puberty, and adult stages, can ultimately affect her fertility.”

Previous research has shown that sperm counts among western men appeared to have halved between 1973 and 2011, with endocrine disruptors cited as a possible cause for the slump along with increasing obesity, smoking and lack of exercise.

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Among women, the picture is more complicated. Globally, the number of children an average woman gives birth to in her lifetime has declined from 4.7 in 1950 to 2.4 by 2017 - but this 'fertility rate' is also a measure of healthcare and social trends.

Nonetheless, Prof Fowler believes there is evidence that more women are struggling to conceive.

He said: "It's highly controversial. It's one of the areas still under considerable debate and research, but in my view we are swinging to that increasingly becoming correct.

"Of course it's much harder to be sure of fertility in women than men, because obviously in men your can just do a sperm count.

"Fertility for the woman is much more complicated because it has to extend right to successful pregnancy, so it's much harder to prove.

"One of the big difficulties is that fertility is measured by the numbers of children, but of course there's a strong social element to that as well.

"But just things like if the chemical makes a woman more likely to be overweight, that will affect her fertility."

The researchers in Aberdeen will use samples of human ovary tissue taken from children with cancer, as well as tissue samples from IVF patients, and examine the effect of some know endocrine disruptor chemicals on these tissues.

They will repeat the experiment in rats and using cells grown in the lab to examine, for example, how these endocrine disruptors affects cells' response to the female hormone oestrogen.

"We will put these three strands together and work out the key pathways that take you from exposure to the chemical to an adverse outcome - which might be reduced fertility," said Prof Fowler.