Some of the chemicals in plastics may negatively impact fertility, experts warn, while the jury is still out on microplastics.
Phthalates, a group of chemicals used to soften and stabilise various plastics, are causing concern for their links to fertility problems and pregnancy complications.
These chemicals are found in food packaging, cosmetics and medical tubing, amongst other everyday items. Phthalates are absorbed into the body through food, when you breathe, and through skin contact. They have been detected in urine, blood, breast milk, amniotic fluid and semen.
Phthalates are synthetic compounds added to plastics to make them flexible, durable and easier to work with during manufacturing.
There are two kinds, both with big names. DEHP, or di2-ethylhexyl phthalate, is often used in medical products such as IV bags and tubing. DBP, or dibutyl phthalate, is found in cosmetics, nail polish, adhesives and even printer ink.
Then there are others that are present in food packaging, kids’ toys, detergents and can even be traced in some medicines.
Because they are not chemically bound to the plastic, phthalates can separate from the plastic and leak out, so to speak. This is why they are often discovered inside the human body.
Negative effects on reproductive systems
“Exposure to some of these chemicals, especially DEHP and DBP, has been shown to have negative effects on both male and female reproductive systems,” said medical doctor and psychologist Dr Jonathan Redelinghuys. “They are linked to decreased fertility and have also been associated with preterm birth, ovarian dysfunction and endometriosis.”
Scientific reviews have shown that phthalates act as endocrine disruptors, interfering with the body’s natural hormone production. In women, higher amounts of phthalates have been linked to lower levels of the female hormone oestrogen and higher levels of the hormones that control ovulation.
This is the same pattern doctors see in women whose ovaries are not working properly. A review in the academic publication Environmental Research this year reported that amongst couples undergoing in vitro fertilisation, elevated levels of these chemicals were associated with poorer egg and embryo quality as well as lower pregnancy rates and reduced chances of live birth.
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The placenta is also at risk, research suggests. Laboratory studies show that phthalates can cause stress and inflammation in placental tissue. These are factors in complications such as preterm labour.
A 2020 study by Frontiers in Public Health linked phthalate exposure in pregnant women to reduced vitamin D levels. This deficiency can impact fetal growth, slowing and disorders like hypertension.
May slow foetal growth
The thyroid gland’s workings, which regulate growth and brain development during pregnancy, can also be impacted. A study published this year in the International Journal of Hygiene and Environmental Health found that a mom’s exposure to phthalates disrupted thyroid hormone levels.
“Because the foetus depends entirely on the mother’s thyroid hormones in the first trimester,” said Redelinghuys, “interference at this stage of shaping life may affect neurodevelopment of the baby.”
Men are also not immune to the effects of this compound. Research has linked higher phthalate exposure to lower sperm counts. Phthalates can make sperm move less effectively and can also change the shape of the swimmers.
These chemicals can also cause damage to the DNA inside sperm, which raises the risk of problems with embryo development even if fertilisation takes place.
“Phthalates are not confined to female reproductive health,” Redelinghuys said. “Male fertility outcomes are also being reported, with measurable declines in sperm quality amongst men with higher levels of exposure.”
Plastics may be all-round sinners. Unlike phthalates, which are chemical add-ons, microplastics are physical fragments of plastic. Apart from widespread environmental concerns already well documented, a study in 2024 identified microplastics in human testicular tissue and semen.
“Evidence pointing to negative reproductive outcomes is emerging,” said Redelinghuys. “Although research has not yet reached the stage of establishing direct causal effects.”
More research needed on microplastics
“The challenge is,” said Redelinghuys, “that contact with phthalates remains unavoidable.”
A review in Environmental Health Perspectives last year noted that exposure is widespread across all populations.
“Phthalates are in everyday items that people cannot realistically avoid,” Dr Redelinghuys said. “That makes the evidence of their impact on fertility and pregnancy outcomes especially important for public health.”
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