Global plastic product manufacturing doubled between 2000 and 2019. Our reliance on products made from or packaged in plastic has increased human exposure to hundreds of synthetic compounds. Exposure to plastic could have a negative influence on human male fertility. What do we know about how these compounds could influence male reproduction, and what advice can be given to men seeking fertility?
Compounds in plastics with the potential to disrupt hormones and fertility
There are many compounds in plastic that have been linked with negative effects on reproduction. Some of these compounds are classified as endocrine-disrupting chemicals (EDCs) that can interfere with the production or action of hormones, often possessing the ability to interfere with androgen and oestrogen-dependent processes. Male sexual development and function rely on a fine balance of hormones throughout life, and therefore male fertility is potentially vulnerable to exposure to plastic compounds that are known EDCs.
Some of the most abundant and well-known compounds with endocrine-disrupting potential in plastic include bisphenol A (BPA) and phthalates which are predominant in clear and/or flexible plastics such as food packaging. With the widespread negative attention of BPA products, many food plastics are now marketed as BPA-free; however, these products contain BPA replacement compounds that have equivalent endocrine-disrupting properties to BPA.
Although EDCs in the environment tend to be present at very low levels, humans are now likely exposed to multiple EDCs on a daily basis. Increasing daily exposure to plastic compounds and EDCs could have synergistic or cumulative effects on the human body and on reproduction.
How do these compounds in plastics get into the human body?
Plastic compounds are ingested after leaching into food and liquids. There are also many plasticizers in the products we handle and use, such as BPA in the paper used for shopping receipts and phthalates in personal care products. Environmental compounds can cross the placenta in pregnant women and potentially influence the developing fetus.
Compounds in plastic enter the human body at appreciable levels. Most adults have BPA in their urine. Phthalates are also widely detected in humans, and their ability to leach out of plastic is well known. Humans also ingest significant quantities of plastic particles known as microplastics.
What do we know about how plastics could affect male reproduction and fertility?
There are different ‘windows of vulnerability’ during male sexual development and adult life where testis development and function could be compromised by environmental exposures and endocrine disrupters.
Perhaps the most vulnerable time is during fetal testis development, where androgen-mediated actions are important for normal development. Testicular descent during the final weeks of gestation can also be affected by endocrine disruption, leading to cryptorchidism, which can affect later fertility. Adult fertility relies on normal pubertal development of the testis and the establishment and maintenance of the hypothalamic-pituitary-testis axis.
There are multiple mechanisms by which EDCs in plastics could interfere with testis development and function. For example, BPA can interfere with testosterone production in animals by disrupting both Leydig cell numbers and the normal function of the hypothalamic-pituitary-testis axis. BPA, phthalates and other compounds in plastics have negative impacts on multiple aspects of male reproductive function in laboratory animals.
Compounds in plastics can alter the sperm epigenome, leading to heritable changes in the offspring that are associated with adverse outcomes such as obesity and reproductive organ disease.
What do we know about the ability of plastics to affect human male infertility?
Despite many studies revealing multiple ways compounds in plastic could influence male reproduction, it is much more difficult to dissect the cause and effect on human male reproduction.
Human studies are largely epidemiological, examining an association between higher exposure to a substance and the appearance of a particular abnormality. The expense and difficulty of undertaking large-scale, well-controlled human population studies make it extremely difficult to determine the effects of specific plastic compounds on male reproduction. So, while plastic-derived compounds could feasibly interfere with human male reproductive development and function, it will be difficult to pinpoint the exact compounds that could cause harm.
To date, there is little mechanistic evidence from human studies to support specific interventions that could improve a man’s sperm count. A single cause-and-effect relationship between a particular compound in plastic and human male fertility may be unlikely; rather, human male reproductive abnormalities will likely have multiple causes.
What should I tell my patients?
Men seeking fertility could be advised that there is limited evidence in humans that exposure to plastics in food and the environment can reduce their fertility. However, many plastics used in daily life contain compounds with endocrine-disrupting properties that reduce fertility in experimental animals.
Men who inquire about ways to help increase their chances of conceiving a healthy baby could be advised that reducing their exposure to plastics, particularly plastic food packaging, may reduce their exposure to chemicals with known endocrine-disrupting properties.
Specific advice could include 1) avoid buying food wrapped in clear plastic (or wash these foods well before use), 2) avoid storing and reheating food in plastic-based products and 3) use plastic-free water bottles.