Infertility

 What we know
 Incidence
 Environmental risk factors

What we know

Infertility is a disorder of the reproductive system diagnosed when a couple fails to have a child after one year of unprotected, well-timed intercourse, or when the woman suffers multiple miscarriages. Infertility cases are linked to both male and female problems. Male problems include low sperm count and sperm abnormalities, whilst female problems are linked to ovulation, thyroid irregularities, polycystic ovarian syndrome and fallopian tube obstruction.

Infertility has many causes. It can be caused early in fetal life when a genetic mutation, a chemical insult or a hormonal imbalance disrupts the delicately balanced mechanisms that guide the development of the reproductive tract. Alternatively, it can occur in adulthood due to diseases that scar the reproductive tract, cause hormonal imbalances or induce harmful immune responses. Infertility also increases with age.

Incidence

The World Health Organisation (WHO) estimates that worldwide 80 million people are affected by infertility [1]. In Europe, fertility rates have been below replacement levels for several decades [2].

Figure 1 Trends in total fertility rates in OECD countries [3] To see an enlarged version of the picture, click here and go page 13.

Figure 2. Total fertility rate, French, Dutch and English speaking countries [4] To see the enlarged version of the picture, click here and go page 54.

Figure 3. Total fertility rate (TFR) Scandinavian countries [5] To see the enlarged version of the picture, click here and go page 54.

Figure 4. Total fertility rate (TFR) German Speaking Countries [6] To see the enlarged version of the picture, click here and go page 55.

Figure 5. Total fertility rate (TFR) Southern Europe [7] To see the enlarged version of the picture, click here and go page 55.

Whilst there is little doubt that this is partly due to behavioural elements such as the decision by many couples to delay childbearing for a number of years after reaching sexual maturity, it does not explain why the largest increase in impaired fertility has been in women under the age of 25 [8].

Environmental risk factors

One possible explanation for this comes for a number of studies that report an increase in incidence in the number of conditions that have the potential to undermine fertility, some of which are linked to chemical exposures. For example, European populations show overall upward trends in hypospadias (where the urethral opening is wrongly located on the penis), cryptorchidism (undescended testes), testicular cancer and declining sperm counts, a collection of disorders grouped together under the term “testicular dysgenesis syndrome”, (TDS) thought to have a common fetal origin linked to endocrine disrupting chemicals EDCs. Endometriosis, a chronic disorder that develops when endometrial cells successfully implant and grow in locations in the body outside the uterus is also associated with infertility and linked to EDCs, dioxins and polychlorinated biphenyls (PCBs) [9], [10], [11], [12]. Obesity, another disease that likely plays and important role in infertility, which has dramatically increased in the past two decades, possibly as a result of increased exposure (EDCs) that mimic estrogens.

 For more information on Endometriosis, Testicular Dysgenesis Syndrome, and Testicular Cancer please see the relevant Chemicals Health Monitor web pages.

The EDCs implicated in infertility include phthalates and Bisphenol A, and pesticides such as DBCP (dibromochloropropane) a chemical known to be highly toxic to sperm, and whose use in banana fields caused sterility in male workers and ended in a $600 million settlement against several US companies [13]. Other chemicals of concern include: alcohol; toluene, used in inks, coatings and glues; styrene, used in plastics; solvents; lead; dioxin and cigarette smoke.

Infertility is a complex disorder whose multiple causes are incompletely understood. While further studies into the potential role of chemicals, and into the timing and effect of multi-compound exposures is needed, there is mounting evidence that chemical exposures during fetal and childhood development may impair human fertility. This is supported by animal and wildlife studies that link reproductive effects in fish and reptiles to EDC exposures.

Based on this body of evidence it might be advisable to put in place precautionary public health policies that limit chemical exposures to help reduce the rising incidence of infertility.

 For more information please see the Collaborative on Health and Environment Working Group on Fertility/Early Pregnancy Compromise