Last reviewed 11 May 2021

Gordon Tranter looks at the impact of chemicals, specifically endocrine disruptors, on human reproduction.

Fertility trends

What are the effects of chemicals on reproductive health? Dr Shanna Swan, professor of environmental medicine and public health at Mount Sinai school of medicine in New York City, has been studying fertility trends for the past twenty years to answer that question. Dr Swan and her team of researchers completed a major study in 2017 concerning the sperm count among men. The research, which involved examining 185 studies involving around 45,000 men, the largest and most comprehensive to date, resolved doubts about the earlier findings. It found that sperm levels among men in Western countries have dropped by more than 50% in the last 50 years.

Dr Swan describes the ways in which chemicals in the modern environment are changing human sexuality and endangering fertility on a vast scale in her book Count Down: How Our Modern World is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperilling the Future of the Human Race. Sperm count, fertility, and testosterone levels are declining while pregnancy loss or miscarriage and premature ovarian failure are increasing all at the same rate: 1% per year, which suggests common causes for these problems. In the book, Dr Swan makes a provocative claim: Humans may not have the ability to reproduce naturally for much longer. She estimates that, by 2050, a large portion of the global population will need assisted reproductive technology to procreate.

Insidiously harmful chemicals

Dr Swan claims that the widespread presence of insidiously harmful chemicals in the modern world is threatening the reproductive development and functionality of both humans and other species.

The worst offenders are a number of different types of endocrine‐disrupting chemicals (EDCs) including bisphenol A, phthalates, pesticides, and other environmental chemicals which are everywhere in the modern world. These EDCs have been shown to adversely impact upon male reproductive health chemicals that interfere with the body’s natural hormones.

When absorbed in the body, an endocrine disruptor can decrease or increase normal hormone levels, mimic the body's natural hormones, or alter the natural production of hormones. The persistent and long-term use of EDCs has deleterious effects on human reproductive health by interfering with the synthesis and mechanism of action of sex hormones. Any change during the synthesis or action of the sex hormones may result in abnormal reproductive functions which includes developmental anomalies in the reproductive tract and decline in semen quality.

The presence of EDCs in everyday products such as canned food, water bottles, plastics, cosmetics, fertilizers, children’s toys and many other goods is a great concern for the general population.

Which products are endocrine disruptors?

Endocrine disruptors are found in many everyday products, including some plastic bottles and containers, liners of metal food cans, detergents, flame retardants, food, toys, cosmetics, and pesticides.

Phthalates

Phthalates (esters of phthalic acid) are primarily used as plasticisers to make plastics, particularly polyvinyl chloride (PVC), flexible and pliant. They are found in a wide range of products including electrical cabling, medical devices and toys. Phthalates are also used in other non-PVC applications such as paints, rubber products, adhesives and some cosmetics. Three phthalate esters, di-2-ethyl hexyl phthalate, dibutyl phthalate and butyl benzyl phthalate, are of particular concern because they can decrease the production of male hormones such as testosterone and make the man more likely to be infertile or have a reduced sperm count.

Bisphenol A

Bisphenol A (BPA; 4,4′-dihydroxy-2,2-diphenylpropane) is used for the production of the high-volume thermoplastic polycarbonate by reacting it with carbonyl chloride, (phosgene), or diphenyl carbonate. Polycarbonate plastic is used to make hard plastic items, drink bottles, baby bottles, re-useable water bottles, food containers and other storage containers. Bisphenol A is also used in epoxy resins used for applications such as paints, rubber products, adhesives and some cosmetics. Bisphenol A can leach into food from the protective internal epoxy resin coatings of canned foods and from consumer products such as polycarbonate tableware, food storage containers, water bottles, and baby bottles. It has been found that BPA exposure, particularly occupational exposure, is related to decreased sperm quality in men.

Pesticides

Pesticides also can have adverse effects on human health including on the reproductive potential and endocrine system. Depending on the substance, the effects can include causing decreases in sperm count. Dibromochloropropane, which was used as a pesticide on pineapple and banana plantations, and ethylene dibromide, which was used for fruit fly infestations, have both been found to produce significant decreases in sperm quality.

EDCs and REACH

Over recent years, the European Commission has taken action against endocrine disruptors in line with the different requirements laid down in the relevant legislation. Specific provisions on how to address endocrine disruptors are now included in legislation in the following areas: pesticides, Regulation (EC) No 1107/2009 concerning the placing of plant protection products on the market; biocides, Regulation (EU) No 528/2012 concerning the making available on the market and use of biocidal products; chemicals in general, Regulation (EC) No 1907/2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH); medical devices, Regulation (EU) 2017/745 on medical devices; and water, Directive 2000/60/EC establishing a framework for Community action in the field of water policy.

From 1 January 2021, an independent regulatory regime for REACH is in operation in Great Britain (England, Scotland and Wales). New decisions taken under the EU regime will not apply in Great Britain. Under REACH, endocrine disruptors can be identified as substances of very high concern (SVHCs) alongside chemicals known to cause cancer, mutations and toxicity to reproduction.

Identification of a substance as a SVHC is the first step in the procedure for authorisation or restriction of the use of the substance. Following the UK's exit from the EU the EU REACH Regulation and related legislation, have been replicated in the UK with the necessary changes to make it operable in a domestic context, with decisions on SVHCs made in Great Britain.

Under the Biocidal Products Regulation, active substances, which are considered as having endocrine-disrupting properties will not be approved unless the risk from exposure to the active substance is shown to be negligible or unless there is evidence that the active substance is essential to prevent or control a serious danger to human health, animal health or the environment.

Summary

Inevitably, these results have led to headlines about “Spermageddon” and reference has been made to dystopian science fiction in which our world is afflicted by widespread infertility and childless civilisations are left hovering on the brink of collapse. Children of Men and The Handmaid’s Tale provide perfect examples of these unsettling narratives.

Looking on the positive side, there is considerable degree of consensus that there is a need to take urgent action to address the uncertainties and gaps in the knowledge and potential dangers to human and wildlife populations from endocrine disrupting chemicals. The EU has developed a regulatory system for substances having endocrine-disrupting properties for chemicals as well as for plant protection products, biocides and medical devices and also for the field of water policy. The opinion of the Royal Society of Chemistry is that on the basis of the scientific evidence to date for endocrine disrupting compounds, it is pragmatic and responsible to assure the safety of citizens and wildlife using risk assessment.