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HomeEnvironmental HealthPremature birth rate may be linked to plastics – US study

Premature birth rate may be linked to plastics – US study

Premature births are rising worldwide, and according to researchers, the cause could be synthetic chemicals called phthalates – used in clear food packaging and personal care products.

Past research has demonstrated that phathalates, or “everywhere chemicals” because they are so common, are hormone disruptors that can affect how the life-giving placenta functions. This organ is the source of oxygen and nutrients for a developing foetus in the womb.

“Phthalates can also contribute to inflammation that can disrupt the placenta even more and set into motion the steps of preterm labour,” lead author Dr Leonardo Trasande, director of environmental paediatrics at NYU Langone Health, told CNN.

“Studies show the largest association with preterm labour is due to a phthalate found in food packaging called Di(2-ethylhexyl) phthalate, or DEHP,” he said. “In our study, we found DEHP and three similar chemicals could be responsible for 5% to 10% of all the preterm births in 2018. This could be one of the reasons why preterm births are on the rise.”

The 5% to 10% percentage translated into nearly 57 000 preterm births in the United States during 2018, at a cost to society of nearly $4bn in that year alone, according to the study, published in Lancet Planetary Health.

“This paper focused on the relationship between exposure to individual phthalates and preterm birth. But that’s not how people are exposed to chemicals,” said Alexa Friedman, a senior scientist of toxicology at the Environmental Working Group, or EWG, who was not involved in the study.

“Every day, they’re often exposed to more than one phthalate from the products they use, so the risk of preterm birth may actually be greater,” she said.

The American Chemistry Council, an industry trade association for US chemical companies, told CNN the report did not establish causation.

“Not all phthalates are the same, and it is not appropriate to group them as a class. The term ‘phthalates’ simply refers to a family of chemicals that happens to be structurally similar, but which are functionally and toxicologically distinct from each other,” a spokesperson for the council’s ’s High Phthalates Panel said.

‘Everywhere chemicals’

Globally, about 8.4m metric tons of phthalates and other plasticisers are consumed annually, according to European Plasticisers, an industry trade association.

Manufacturers add phthalates to consumer products to make the plastic more flexible and harder to break, primarily in polyvinyl chloride, or PVC, products like children’s toys.

Phthalates are also found in detergents; vinyl flooring, furniture and shower curtains; automotive plastics; lubricating oils and adhesives; rain and stain-resistant products; clothing and shoes; and scores of personal care products including shampoo, soap, hair spray and nail polish, in which they make fragrances last longer.

Studies have connected phthalates to childhood obesity, asthma, cardiovascular issues, cancer and reproductive problems such as genital malformations and undescended testes in baby boys, and low sperm counts and testosterone levels in adult males.

“The Consumer Product Safety Commission no longer allows eight different phthalates to be used at levels higher than 0.1% in the manufacture of children’s toys and child care products,” Trasande said. “However, not all of the eight have been limited in food packaging by the FDA (US Food and Drug Administration).”

In response to governmental and consumer concerns, manufacturers may create new versions of chemicals that no longer fall under any restrictions. Take DEHP, for example, which has been replaced by newer phthalates called di-isodecylphthalate (DiDP), di-n-octyl phthalate (DnOP), and diisononyl phthalate (DiNP).

Are those safer than the original? That’s not what scientists say they typically discover as they spend years and thousands of dollars to test the newcomers.

“Why would we think that you can make a very minor change in a molecule you are manufacturing and the body wouldn’t react in the same way?” asked toxicologist Linda Birnbaum, former director of the National Institute for Environmental Health Sciences, as well as the National Toxicology Programme. She, too, was not involved in the paper.

“Phthalates should be regulated as a class (of chemicals). Many of us have been trying to get something done on this for years,” Birnbaum said.

Even more dangerous swops

The new research used data from the National Institutes of Health’s Environmental influences on Child Health Outcomes, or ECHO, study, which investigates the impact of early environmental influences on children’s health and development. In 69 sites around the country, expectant mothers and their newborns are evaluated and provide blood, urine and other biological samples to be analysed.

The team identified 5 006 pregnant mothers with urine samples that tested positive for different types of phthalates and compared those with the baby’s gestational age at birth, birthweight and birth length.

Data was also pulled from the 2017-2018 National Health and Nutrition Examination Survey, a government programme that assesses the health and nutritional status of Americans using a combination of interviews, physical examinations and laboratory analysis of biological specimens.

After analysing the information, Trasande and his co-authors were able to confirm past research showing a significant association of DEHP with shorter pregnancies and preterm birth.

Interestingly, however, the research team found the three phthalates created by manufacturers to replace DEHP were actually more dangerous than DEHP when it came to preterm birth.

“When we looked further into these replacements, we found even stronger effects of DiDP, DnOP and DiNP,” Trasande said. “It took less of a dose to create the same outcome of prematurity.”

Dangers of prematurity

A birth is considered preterm if it occurs before 37 weeks of gestation. Because vital organs and part of the nervous system may not be fully developed, a premature birth may place the baby at risk. Babies born extremely early are often immediately hospitalised to help the infant breathe and address any heart, digestive and brain issues or an inability to fight off infections.

As they grow up, children born prematurely may have vision, hearing and dental issues, as well as intellectual and developmental delays. Prematurity can contribute to cerebral palsy, epilepsy, and mental health disorders like anxiety, bipolar disorder and depression.

As adults, people born prematurely may also have higher blood pressure and cholesterol, asthma and other respiratory infections and develop type 1 and type 2 diabetes, heart disease, heart failure or stroke.

All of these medical expenses add up, allowing Trasande and his co-authors to estimate the cost to the US in medical care and lost economic productivity from preterm births to be “a staggering $3.8bn", said EWG’s Alexa Friedman. “But the real cost lies in the impact on infants’ health.”

There are additional steps that can be taken to reduce exposure to phthalates and other chemicals in food and food packaging products, according to the American Academy of Paediatrics’ policy statement on food additives and children’s health.

“One is to reduce our plastic footprint by using stainless steel and glass containers, when possible,” said Trasande, who was lead author for the AAP statement.

“Avoid microwaving food or beverages in plastic, including infant formula and pumped human milk, and don’t put plastic in the dishwasher, because the heat can cause chemicals to leach out,” he added. “Look at the recycling code on the bottom of products to find the plastic type, and avoid plastics with recycling codes 3, which typically contain phthalates.”

Study details

Prenatal phthalate exposure and adverse birth outcomes in the USA: a prospective analysis of births and estimates of attributable burden and costs

Leonardo Trasande, Morgan Nelson, Akram Alshawabkeh, Emily Barrett, Jessie Buckley, Dana Dabelea, et al.

Published in Lancet Planetary Health on February 2024

Summary

Background
Phthalates are synthetic chemicals widely used in consumer products and have been identified to contribute to preterm birth. Existing studies have methodological limitations and potential effects of di-2-ethylhexyl phthalate (DEHP) replacements are poorly characterised. Attributable fractions and costs have not been quantified, limiting the ability to weigh trade-offs involved in ongoing use. We aimed to leverage a large, diverse US cohort to study associations of phthalate metabolites with birthweight and gestational age, and estimate attributable adverse birth outcomes and associated costs.

Methods
In this prospective analysis we used extant data in the US National Institutes of Health Environmental influences on Child Health Outcomes (ECHO) Program from 1998 to 2022 to study associations of 20 phthalate metabolites with gestational age at birth, birthweight, birth length, and birthweight for gestational age z-scores. We also estimated attributable adverse birth outcomes and associated costs. Mother–child dyads were included in the study if there ere one or more urinary phthalate measurements during the index pregnancy; data on child's gestational age and birthweight; and singleton delivery.

Findings
We identified 5006 mother–child dyads from 13 cohorts in the ECHO Program. Phthalic acid, diisodecyl phthalate (DiDP), di-n-octyl phthalate (DnOP), and diisononyl phthalate (DiNP) were most strongly associated with gestational age, birth length, and birthweight, especially compared with DEHP or other metabolite groupings. Although DEHP was associated with preterm birth (odds ratio 1·45 [95% CI 1·05–2·01]), the risks per log10 increase were higher for phthalic acid (2·71 [1·91–3·83]), DiNP (2·25 [1·67–3·00]), DiDP (1·69 [1·25–2·28]), and DnOP (2·90 [1·96–4·23]). We estimated 56 595 (sensitivity analyses 24 003–120 116) phthalate-attributable preterm birth cases in 2018 with associated costs of US$3·84 billion (sensitivity analysis 1·63– 8·14 billion).

Interpretation
In a large, diverse sample of US births, exposure to DEHP, DiDP, DiNP, and DnOP were associated with decreased gestational age and increased risk of preterm birth, suggesting substantial opportunities for prevention. This finding suggests the adverse consequences of substitution of DEHP with chemically similar phthalates and need to regulate chemicals with similar properties as a class.

 

The Lancet Planetary Health article – Prenatal phthalate exposure and adverse birth outcomes in the USA: a prospective analysis of births and estimates of attributable burden and costs (Open access)

 

CNN article – Foods we eat are covered in plastics that may be causing a rise in premature births, study says (Open access)

 

See more from MedicalBrief archives:

 

100 times more nanoplastics in water bottles than thought – US study

 

Study finds microplastics in heart tissues, pre- and post-surgery

 

BPA levels in humans dramatically under-estimated — study

 

 

 

 

 

 

 

 

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