Early prenatal exposure to suspected endocrine disruptor mixtures is associated with lower IQ at age seven
Authors: Eva M. Tanner, Maria Unenge Hallerbäck, Sverre Wikström, Christian Lindh, Hannu Kiviranta, Chris Gennings, Carl-Gustaf Bornehag
The human body’s endocrine system controls many processes through hormones, such as development, behavior, and metabolism. Endocrine Disrupting Chemicals (EDCs) are chemicals or groups of chemicals that alter the way this system normally functions¹. When we are exposed to EDCs, they mimic our natural hormones and disrupt hormone balances².
EDCs can be natural or manmade and include phthalates, bisphenols (BPF, BPA), perfluoroalkyl substances (PFASs), lead, dichlorodiphenyltrichloroethane (DDT), and polychlorinated biphenyls (PCBs)¹. They can be found in many commonly used substances and products, including pesticides, metals, food additives and contaminants, personal care products, plastics, detergents, and toys³. Through these exposure pathways, EDCs can be ingested, inhaled, absorbed through the skin, or passed from mother to child prenatally through the placenta and after birth through breastmilk³. Studies have shown that prenatal EDC exposures are of particular concern, as children’s organs and organ systems are only beginning to form⁴. Previous research has linked prenatal exposure to individual EDCs to developmental abnormalities, learning disabilities, effects on brain, and behavior⁵.
To examine the relationship between early prenatal exposure to multiple EDCs and overall cognitive functioning in early childhood. Prior studies have focused on the effects of singular EDCs, ignoring the reality of being exposed to multiple EDCs simultaneously in daily life.
The researchers used data from a Swedish birth cohort study. 718 mother-child pairs were selected from the data set. Blood and urine samples were collected from the mothers during their first prenatal visit in their first trimester of pregnancy. Twenty-six EDC compounds were included for analysis.
Cognitive functioning was measured through IQ tests given to the children at 7 years of age.
Adjustments were made for possible confounders such as sex, gestational age, mother’s education, mother’s IQ, weight, and smoking status.
IQ scores were 1.9 points lower for boys than girls, suggesting that boys are more affected by prenatal exposure to EDCs. Bisphenol-F (BPF) was the main chemical of concern, having the largest sample weight of 14%. Other chemicals of concern include 3-phenoxybenzoic acid (PBA) and 1,2,3-trichloropropane (TCP).
The study results link higher exposure to multiple EDCs with lower cognitive functioning, particularly among boys. BPF had the highest contribution to the chemical mixture. This suggests that although used as a presumably safer alternative to BPA, BPF exposure to pregnant mothers and young children may not be safe.
Bisphenol F is one of many bisphenols (e.g., Bisphenol S, Z, B, AP, and AF) that were developed as substitutes in response to discovering the harmful associations of BPA exposure and human health⁶. BPA safety has been studied by the U.S. Food and Drug Administration (FDA) since the early 1960s when it was first approved for use in food packaging and food contact materials and applications. In recent years, the FDA has created science boards to continually review the safety of BPA use due to the hundreds of studies being published on its associated health effects⁷.
The scrutiny of BPA has augmented the use of other bisphenols, and these bisphenols have been studied far less than BPA. Many products are marketed with “BPA-Free” labels, leading consumers to trust the safety of the product, but the products might still contain Bisphenol F, S, Z, B, AP, or AF; which may be harmful. The FDA banned BPA from baby bottles and sippy cups in 2012 and regulates its use in other food contact, food packaging, and food applications, but ignores the use of BPA and all other bisphenols in personal care products, medical devices, and dental sealants. The Consumer Product Safety Commission (CPSC) does not provide any information on BPF and the other BPA substitutes even though they are found in thermal cash register receipts, laminate flooring, concrete, water tanks, household appliances, cars, airplanes, sealants, adhesives, grout, and plastics⁸. The Occupational Safety and Health Administration (OSHA) does not provide any regulations or guidelines on BPA substitutes as well.
U.S. Environmental Protection Agency (EPA) has full responsibility for the nation’s chemical management under the Frank Lautenberg Chemical Safety for the 21st Century Act (Lautenberg Chemical Safety Act of 2016). Under this law EPA has authority to require testing of chemical substances prior to their introduction onto the marketplace, and EPA is also mandated to review the safety of chemicals currently in the marketplace (prioritized by volume of use and persistence in the environment). The law requires that EPA perform health-based rather than cost-benefit based assessments of chemicals, and that the agency explicitly considers special groups such as children, pregnant women, and other vulnerable populations, as well as environmental risk⁹.
Despite the authority provided to EPA under this Act, assessments of existing priority chemicals is a very slow process, and the first few conducted have excluded certain chemical uses and exposures from the scope of the risk evaluation. In addition, risk assessments do not consider exposures to multiple substances, such as a mixture of the 26 EDCs as investigated in this research study.
Moreover, in a few cases, when EPA’s finalized risk evaluation indicated the need for regulation, that regulation has been and is still unnecessarily delayed. In the meantime many chemicals currently in common use, such as BPF and other bisphenols, remain unregulated, posing potential health and developmental risks to children.
EPA, FDA, CPSC, and OSHA need to keep current on the latest independent scientific research--including important epidemiological studies, and the agencies need to assess risk based on real world exposure scenarios if they are to effectively protect children’s health. In the meantime, states are taking matters into their own hands.
In Washington state, new legislation on toxic chemicals in consumer products was recently signed into law on May 8, 2019¹º. The Pollution Prevention for our Future Act is considered the strongest policy in the nation for toxic chemicals in consumer products¹¹. It is progressive in the following ways:
- Instead of using an individual chemical approach, state agencies will group chemicals into classes (e.g. phthalates, PFAS, PCBs, bisphenol compounds, etc.) to prevent companies from switching from one toxic chemical to another similar chemical.
- Banning or restricting of chemicals is authorized by the Department of Ecology after a safer alternative is determined.
- Specific action timelines with oversight to keep the program on track and making progress.
Washington’s law can serve as a model for other states looking to better safeguard children’s health in the face of the current weak implementation of the new chemical safety law at the federal level.
- Editor's Highlight: Transcriptome Profiling Reveals Bisphenol A Alternatives Activate Estrogen Receptor Alpha in Human Breast Cancer Cells.