If you want kids, watch out for plastics
The chemicals in micro-and nano plastics (MNPs) cause a plethora of health
impacts including harming people’s hormonal systems leading to infertility, and
neurological and behavior disorders among other issues, says a new review which unpacks the mechanisms of how
plastics harm health.
Typically, people consume microplastics from contaminated
food and drinking water, ingesting around 50,000 particles each year. People can also
inhale micro- and nano plastics and absorb them through skin contact. Most
microplastics in the atmosphere come from the wear
and tear of vehicle tires and brake pads. Researchers estimate that the
harmful health effects from toxic chemicals in microplastics cost the United
States nearly $250 billion in health care expenses in one
year.
To tackle the plastic epidemic and its health harms,
scientists and health advocates are pushing for world leaders to commit to curb plastic
production in a legally binding United Nations treaty due to be voted
on next month in Geneva, Switzerland.
The plastics and fossil fuel industry objects to curbs on production, arguing instead for more recycling. But scientists and pollution advocates say that very little plastic is ever recycled and doing so adds to the spread of toxic chemicals in the plastics.
“We are already seeing the impacts of plastic pollution on
our health and our children’s health….The solution is to cap and reduce plastic
production,” said Tracey Woodruff, Professor and Director of the Program
on Reproductive Health and the Environment, University of California, San
Francisco.
“We are already seeing the impacts of plastic pollution on our health and our children’s health….The solution is to cap and reduce plastic production,” said Tracey Woodruff, Professor and Director of the Program on Reproductive Health and the Environment, University of California, San Francisco.
Messing with the endocrine system
The tiny bits of plastic contain endocrine-disrupting
chemicals which can accumulate in body tissues and organs, such as ovaries and
testes, where they bind to hormone receptors and interfere with their function,
the review authors wrote. The chemicals also mess with key parts of the body’s
endocrine system including the hypothalamus – an area of the brain that helps
regulate hormones and the nervous system, and controls body temperature and
blood pressure, among other central processes. For example, studies have found
that endocrine disrupting chemicals interfere with the molecules produced by the hypothalamus that
signal to the body when it is time to eat or sleep.
MNPs also affect several other organs involved in the
endocrine system, wrote the review authors. These include the pituitary gland
in the brain – which makes hormones involved in reproduction and fertility –
and the thyroid gland found in the neck, which produces hormones that control
how the body uses energy. Long-term exposure to MNPs harms the development and
function of the thyroid gland, the review authors wrote. Studies show that rats fed a daily diet of
nanoplastics and polystyrene for 5 weeks produced less of two key thyroid
hormones known as thyroxine (T4) and triiodothyronine (T3).
Endocrine disrupting chemicals mainly interfere with the
function of the pituitary gland by messing with the hypothalamus. They reduce
levels of hormones important to the reproductive system such as follicle
stimulating hormone which is involved in the production of sperm and eggs. This
can lead to infertility and possibly cancer of the uterus, the review authors
write.
Harming reproduction
Reproductive organs comprising the ovaries and testes are
very sensitive to the damaging effects of endocrine disrupting chemicals in
micro- and nanoplastics, wrote the review authors. Studies
in rodents exposed to microplastics found that the plastics build up
in uterine tissue and ovaries. They also found a drop in the production of
proteins that provide structural support for cells and are involved in cell
movement. The ovaries also weighed less, and produced fewer mature follicles –
the sacks that contain developing eggs. Tests in mice that drank water
contaminated with microplastics, found that mice ovaries showed signs of oxidative stress – a condition where
antioxidants in the body are unable to combat free radicals – unstable and
highly reactive molecules that can damage cells.
Microplastics are linked to a decrease in pregnancies and an
increase in offspring mortality, wrote the review authors.
Microplastics also cause oxidative stress and inflammation
in the male testes. Studies in mice that were fed polystyrene microplastics for
28 days found a reduction in sperm number and quality and lower testosterone
levels. These findings suggest MNPs could be contributing to the continuing
decline in male fertility rates seen over the last 80-years.
Better controls on plastic pollution
Plastic production and use continues to grow as does the
evidence of its harm to human health, particularly in vulnerable populations
like children and pregnant women, the review authors wrote. Further research is
needed into the long term effects of micro- and nanoplastics, and to better
understand the mechanisms through which they harm health. In the meantime, the
authors call for limits on the mass production of plastics and plastic
additives containing endocrine disrupting substances.
The Endocrine Society, a global professional organization of
endocrinologists, says the mounting evidence of the health impacts of plastics
and the toxic chemicals they contain is not keeping pace with current
regulations to control their production and use.
The International Pollutants Elimination Network (IPEN) says
a legally binding global treaty is needed to curb plastic production and
protect human health.
Bjorn Beeler, IPEN International Coordinator said in a
statement, “More plastic production means more pollution. That’s why the Treaty
also needs to include provisions to cap and reduce plastic production, and not
rely on false promises about failed solutions, like plastic recycling.”
