Article analyzes the toxic effects of the exposure of pregnant women to pollutants

A review article led by researchers from the Oswaldo Cruz Institute (IOC/Fiocruz) analyzes scientific evidence on the impact of the exposure of pregnant women to two types of chemical substances, which can damage the formation of the central nervous system of babies. Published in the Journal of Hazardous Materials, the study was carried out in partnership with scientists from the Florida International University and the University of Miami in the United States.

Used in various industrial processes and present in everyday products – such as non-stick pans, fire-fighting foams, waterproof and stain-resistant fabrics, food packaging, and insecticides – perfluoroalkyl and polyfluoroalkyl substances (PFAS) are called ‘forever chemicals’ due to their high resistance to degradation.

In recent years, these elements have become a cause for concern: the most produced and most studied molecules in this group have been associated with serious health risks, which has led to restrictions on the production and use of three of these compounds.

Besides PFAS, the article also discusses polychlorinated biphenyls (PCBs). In Brazil, the best-known commercial product with this type of compound was ascarel, used as an insulating fluid in industries, electrical transformers, capacitors, hydraulic systems, among other applications.

Considered highly toxic, PCBs have been banned in several countries, including Brazil, which established the ban in 1981. Despite this, the molecules remain in the environment and can still be found in old equipment. In the article, the researchers draw attention to the widespread dissemination of PFAS and PCBs in the environment, being found in water and soil samples in several countries, as well as in fish, wild animals, dairy products, and the human body.

"PFAS and PCBs are persistent organic pollutants that can be carried long distances by water and air and accumulate in nature and in living organisms. For example, PCBs have already been found in polar bears and there are records of PFAS in the Arctic and Antarctic," points out Rachel Ann Hauser-Davis, researcher at the IOC/Fiocruz's Environmental Health Assessment and Promotion Laboratory.
According to the scientists, humans are chronically exposed to low doses of these compounds, e.g. through contaminated water or food.

"Some studies suggest that this chronic exposure can cause damage, but this is a type of research that is still ongoing. On the other hand, research into exposure to relatively high levels of these substances, as occurs with workers in some industries, clearly shows their negative effects," explains Maria Carolina Peixoto Rodrigues, post-doctoral student at IOC/Fiocruz.

Among the factors that led to the restrictions on PCBs and three compounds from the PFAS group are: cancer risk, immunity problems, hormonal dysfunction, fertility changes, impact on fetal development, among others.

A review of the scientific literature showed that exposure to the substances during pregnancy has been consistently associated with adverse effects on the development of babies' central nervous systems.
"Research shows that PCBS and PFAS are capable of crossing the blood-brain barrier, which protects the brain, and can cause neurological damage to the fetus through different mechanisms," says Daniel Adesse, researcher at the IOC's Structural Biology Laboratory.

Biological mechanisms

The scientific literature review was carried out with the aim to understand the current state of knowledge, in view of research recently started at the IOC to investigate the effects of exposure to persistent organic pollutants, through experiments in cell cultures and experimental models.

The researchers note that, to date, studies on PFAS have focused mainly on the three compounds that are already being restricted, which are known by the acronyms PFOS, PFOA, and PFHxS.
"There is a significant gap in the understanding of the effects of other substances in this group, which continue to be widely used," Rachel points out.

Among the research already published are studies with human beings that have shown a correlation between gestational exposure levels to these pollutants and the risk of neurodevelopmental disorders, including cognitive dysfunction, impulsive behavior, inattention, anxiety, and depression.

"These studies cannot confirm a causal relationship, but they do show an association. Moreover, in the laboratory, tests on animals and cell cultures show evidence of changes caused by PFAS and PCBs that can damage the development of the nervous system," says Rachel.

The alteration of the blood-brain barrier is one of the processes highlighted. To protect the brain, the wall of the cerebral blood vessels forms a highly selective semi-permeable barrier, which allows cells and molecules necessary for the organ to pass through, but blocks various substances present in the bloodstream.

Studies indicate that PFAS and PCBs damage the integrity of this barrier, allowing toxic molecules to reach neurons and other brain cells. "Alterations in the blood-brain barrier are associated with various neurological disorders. It is crucial to advance research into the functional consequences of the disturbance caused by PFAS and PCBs and into the damage recorded at different times during pregnancy," says Maria Carolina.

Research also indicates that the compounds can impair the proliferation, migration, and differentiation of neurons and cause oxidative stress and inflammation of brain tissue. Hormonal changes and alterations in the maternal gut microbiota may also contribute to failures in regulating the development of the central nervous system in babies.

Regulations

The researchers highlight that most studies on environmental contamination and human exposure to PFAS and PCBs have been conducted in countries in the Northern Hemisphere, with limited information available on the Global South. In Brazil, the ban on the trade, production, and use of PCBs has been in effect since 1981, and the elimination of old contaminated equipment was mandated by a law in 2021, with deadlines that may extend until 2028.

Furthermore, regulations from the National Environment Council (Conama), the Brazilian Health Regulatory Agency (Anvisa), and the Ministry of Agriculture, Livestock, and Supply (Mapa) set limits for PCB contamination in soil, various water sources, and in food for human and animal consumption.

With regard to PFAS, the production and use restrictions set out by the Stockholm Convention for PFOS, PFOA, and PFHxS have been ratified in Brazilian laws. However, there is a lack of regulation to reduce the population's exposure to compounds in this group.

"Last year, the United States set limits for six types of PFAS in drinking water. The European Union has a directive that limits the total amount of PFAS in drinking water. In Brazil, there is a bill pending decision to regulate PFAS, but so far we have no systematic monitoring or legislation in place on this matter," says Daniel.

In some places, broader restrictions on PFAS are under discussion. In 2021, the state of Maine, in the United States, passed legislation setting a deadline of 2030 to ban the compounds.

Since 2023, the European Union has been assessing a proposal presented by Germany, the Netherlands, Denmark, Sweden, and Norway to ban PFAS in consumer products. "It is important to discuss the most appropriate regulations based on the available evidence and to advance research, including to try to remedy environmental contamination that has already occurred, as these substances can remain in the environment for hundreds of years," adds Rachel.