PFAS and ADHD

by Vaishnavi Raman and Charlie Xiang

PFAS

Perfluoroalkyl/Polyfluoroalkyl (PFAS) are a group of chemicals which contain strong carbon-fluorine bonds. PFAS are found in industrial and consumer products due to their resistance to water, grease, and heat. PFAS are also known as forever chemicals because their strong intermolecular bonds make the chemical difficult to break down. PFAS contaminate drinking water due to runoff and fire fighting foams. The chemicals accumulate in the body causing detrimental health effects: cancer, liver damage, thyroid disease, developmental effects in children, etc. Research has linked PFAS exposure to the cause of multiple neurological disorders: memory loss, depression, ADHD, etc. 

ADHD

Attention Deficit Hyperactivity Disorder (ADHD) is a common neurological disorder, categorized into inattentive and hyperactive. Symptoms include lack of focus, disorganization, and forgetfulness. ADHD is a dysfunction in frontal lobe activity, affecting decision making and emotional regulation. It impairs the ability to function and socially interact (Magnus et. al, 2023).

Johanna Inhyang Kim conducted a study in 2023 to investigate the link between PFAS exposure and development of ADHD. The study focused on pregnant women in their second trimester. Urine samples were used to assess exposure to environmental endocrine-disrupting chemicals. Later, there were follow up physical exams for the children at ages 2, 4, and 8. They took blood and urine samples from the children, and mothers answered questionnaires on their child’s health. There were a total of 521 children used in the final analysis. 

PFAS exposure levels were measured using high-performance liquid chromatography, detecting 14 PFAS compounds. PFAS detection rates varied, with 6 compounds showing higher detection frequencies in the final analysis. (Kim et. al, 2023)

To quantify ADHD, they used the ADHD Rating Scale IV (ARS). ADHD symptoms are usually identified around 8 years old. Parents used a Likert Scale with each item correlating Diagnostic and Statistical Manual of Mental Disorders IV. Higher scores indicate more problematic behavior (Kim et. al, 2023).

Figure 1.: Confidence Interval Plot Showing Association Between PFAS Exposure at Age 2 and 4 and 1st Quartile of ARS Scores at Age 8

Figure 1a shows an inverted U-shaped relationship between PFAS exposure at age 2 and ARS scores at age 8. However, Figure 1b shows no similar non-linear relationships found for PFAS exposure at age 4. The greatest changes in ARS scores were observed in the 2nd quartile for PFOA, PFDA, PFUnDA, and PFHxS, and in the 3rd quartile for PFNA and PFOS. Original Publication from Johanna Inhyang Kim.

The results show exposure at 2 years old was significantly associated with ADHD symptoms. Six PFAS compounds showed U-shaped associations. U-shaped associations indicate moderate PFAS exposure had higher ADHD symptom scores than low and high PFAS exposure. Children in the second and third quartile had higher ARS scores than those in the first quartile. Findings suggest age 2 is a vulnerable period for PFAS neurotoxicity, with stronger associations at lower exposure levels (Kim et. al, 2023).

Summary

Research exposes the detrimental neurological effects PFAS exposure causes. Effects can occur as young as 2 years old and persist through adulthood. These studies are helpful in promoting the creation of policies to decrease PFAS exposure (Kim et. al, 2023).

References

1. Kim J. I., Kim B., Lee Y., Shin C. H., Hong Y., Døssing L. D., Hildebrandt G., Lim Y., Association between early-childhood exposure to perfluoroalkyl substances and ADHD symptoms: A prospective cohort study, Science of The Total Environment, Volume 879, 2023, 163081, https://doi.org/10.1016/j.scitotenv.2023.163081.

2. Magnus W., Nazir S., Anilkumar A. C., Shaban K., et.al, Attention Deficit Hyperactivity Disorder, National Library of Medicine, 8 August 2024, https://www.ncbi.nlm.nih.gov/books/NBK441838/