May 12, 2014

expert reaction to endocrine disrupting chemicals and male fertility

Researchers publishing in EMBO Reports looked at the effect of various endocrine-disrupting chemicals on human sperm function reporting they may have a negative impact on fertility. 

Prof Sir Colin Berry, Emeritus Professor of Pathology, Queen Mary University of London (QMUL), said:

“The difficulty here is extrapolating from an in vitro test to an in vivo situation. At the levels apparently tested, some of the compounds involved do not affect fertility or pregnancy outcomes in the animals in which they have been tested. The authors suggest that this might be used as a screening test – it would be necessary to validate it first! The next stage might be to see if rodent sperm is similarly affected and, crucially, to see if affected rodent sperm are unable to fertilise rodent eggs.”

Dr Allan Pacey, Senior Lecturer in Andrology, University of Sheffield, said:

“Scientists have for many years been concerned about the possibility that man-made chemicals in the environment may be having a negative impact on male fertility. To date this has been largely from the point of view that so called ‘endocrine disrupting chemicals’ may be causing men to produce fewer sperm than they should. However, there have also been some hints that chemicals could also affect the function of sperm directly in some way, meaning that they work less well when they are trying to reach an egg or fertilise it.

“Therefore the paper by Schiffer et al., (2014) is most intriguing and it has used a novel system of examining the effect of individual chemicals, and cocktails of chemicals, on how sperm behave in the laboratory. They suggest that many common chemicals can affect sperm function by changing the concentration of calcium inside sperm. We already know that sperm calcium concentrations are a key regulator for how they swim and interact with the egg; and these are just two of the many jobs sperm have to do before conception can occur.

“However, whilst the data presented appears to be robust, we should be very careful about how we interpret the data and we should avoid any knee-jerk reactions to public health policy or advice to patients. Although sperm calcium changes may be seen in the laboratory, this is a long way removed from what might happen in living people. Whilst the authors have attempted to use concentrations of these compounds that are found in bodily fluids, this data is incomplete and the environment of the reproductive tract is quite unique and is not the same as blood, urine or saliva.

“Moreover, we know from epidemiological evidence from other work that I am involved with (e.g. Cherry et al., 2008; Povey et al., 2012) that men are exposed to relatively few chemicals or lifestyle factors that affect their semen quality. Therefore, I would want to see these research findings replicated in a suitably large epidemiological study before I would be convinced that they are a genuine hazard to reproductive health.”

References from Allan Pacey:

Cherry, N., Moore, H., McNamee, R., Pacey, A., Burgess, G., Clyma, J-A., Dippnall, M., Baillie, H., Povey, A., and participating centres of CHAPS-UK (2008) Occupation and male infertility: glycol ethers and other exposures.  Occupational and Environmental Medicine. 65: 708-714.

Povey, A.C., Clyma, J.A., McNamee, R., Moore, H.D., Baillie, H., Pacey, A.A., Cherry, N.M.; Participating Centres of CHAPS-UK. (2012) Modifiable and non-modifiable risk factors for poor semen quality: a case-referent study. Human Reproduction 17: 2799-2806.

Prof Tony Dayan, Emeritus Professor of Toxicology, University of London, said:

“This work on certain effects of a range of chemicals on specific functions within sperm represents a new and largely untried means of investigating effects on important functions in sperm.

“Whether the results can reveal significant toxic risks of chemicals on reproduction depends on whether sperm in humans are exposed to active concentrations of the substances. The evidence cited is very limited, it depends on considerable extrapolation and requires strong confirmation that is not provided.

“This publication shows the need to compare the effects claimed with the extensive information already available about the named substances and their effects in humans and established laboratory studies.”

Declared interests

Dr Allan Pacey’s declared interests are: Chairman of the Executive Committee of the British Fertility Society, Chairman of the advisory committee of the UK National External Quality Assurance Schemes in Andrology, member of the Advisory Council of the National Gamete Donation Trust, member of a working group of the Advisory Committee on the Safety of Blood Tissues and Organs of the Department of Health (all unpaid).  Also, consultancy for the Human Fertilisation and Embryology Authority, The Nuffield Council, University College London Hospitals, the World Health Organisation, and Capital K Pictures (paid consultancy with all money going to University of Sheffield).

‘Direct action of endocrine disrupting chemicals on human sperm’ by Christian Schiffer et al. was published in EMBO Reports on Monday 12 May 2014.