Human sewage harms sheep foetuses

Sheep have a long gestation period similar to that of humans

Sheep grazing on fields fertilised with human sewage produce lambs with fertility problems, according to research by Scottish scientists.

A study by the University of Aberdeen suggests chemicals which enter the human body and are then excreted can harm the foetuses of mammals.

The scientists hope the research will help pinpoint the most vulnerable stages of foetal development.

They have applied for funding to study the human implications of the findings.

If we can definitely establish that environmental chemicals are important in triggering these diseases, then we might be able to produce better treatments Dr Paul Fowler

The group hope that further funding from the Wellcome Trust will allow them to look more closely at the chemicals involved and their possible impact on human development.

Study leader Dr Paul Fowler, from the University of Aberdeen, told the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in the French city of Lyon that it was possible environmental chemicals affect the development of the foetus.

Increased production of industrial and agricultural chemicals in recent decades has coincided with reports of breeding problems in wild animals.

Sludge chemicals

Fertility also appears to be declining among humans and there has been a rise in reproductive defects in newborn babies.

Most studies investigating these trends have looked at short-term exposure to high doses of single compounds, usually in mice and rats.

Dr Fowler's team wanted to examine the effect of long-term, low-level exposure to a "cocktail" of chemicals and heavy metals such as that found in human waste.

Sheep were chosen because they have a long gestation period similar to that of a human.

Dr Fowler said the group had examined the ovaries from the foetuses at day 110 of gestation, the equivalent of week 27 in human pregnancy.

Reduced testosterone

They found that the ovaries from the foetuses where the mother was grazing in sewage sludge fields contained fewer eggs as well as a number of protein abnormalities.

"These differences could have implications for problems such as cancer in later life," Dr Fowler said.

Researchers also found reduced testosterone and testis cell numbers in male sheep foetuses exposed to the sludge chemicals.

There is still disagreement over importance of environmental chemicals to cancer, obesity, infertility and other complex conditions with multiple causes.

"We hope our research will help in the drive for evidence-based policy making on this issue," said Dr Fowler.

"If we can definitely establish that environmental chemicals are important in triggering these diseases, then we might be able to produce better treatments."