Dr Philippe Grandjean
Professor of Environmental Medicine at the University of Southern Denmark and Harvard. The researcher who proved that PFAS suppresses the immune systems of children.
Dr Philippe Grandjean is Professor of Environmental Medicine at the University of Southern Denmark and Research Professor at the University of Rhode Island. He previously held a position at the Harvard School of Public Health. He is one of the world's leading authorities on the health effects of environmental chemical exposure, with a particular focus on PFAS and their effects on the developing immune system. His research spans more than four decades and has been published in the New England Journal of Medicine, JAMA, Environmental Health Perspectives and dozens of other peer reviewed journals. He is founding editor of the journal Environmental Health. His work on the Faroe Islands population, where PFAS exposure has been documented in children from birth, produced the landmark evidence linking PFAS to immune suppression that helped drive the push for binding regulatory limits on forever chemicals internationally.
The Research That Changed Everything
Grandjean's most significant contribution to public health is a series of studies conducted on children in the Faroe Islands, an archipelago in the North Atlantic where a traditional diet high in seafood and whale meat results in elevated PFAS exposure. This population provided a natural study group that allowed him to measure PFAS body burdens from birth and track their effects across childhood.
The findings were stark. Children with higher PFAS blood levels at ages five and seven produced significantly fewer antibodies following routine childhood vaccinations for tetanus and diphtheria. In some cases, antibody concentrations fell below the threshold considered protective against disease. A doubling of PFAS exposure was associated with halving of the vaccine antibody response.
A sizable proportion of fully vaccinated children may have vaccine responses that provide incomplete protection against disease due to PFAS immunotoxicity. This finding may be of substantial public health relevance not just in regard to specific vaccine responses but possibly also in regard to broader immune function.
Grandjean et al., JAMA, January 2012
The studies were replicated and extended across multiple subsequent research groups and populations. Grandjean himself followed the Faroe Islands cohort into adolescence, confirming that the immune suppression effects persisted. A 2024 Danish study extended the findings to COVID-19 vaccination responses in adults, finding reduced antibody responses in people with higher historic PFAS exposure.
Key Research and Findings
Grandjean et al., JAMA, 2012. The landmark study. 656 children from the Faroe Islands birth cohort. Higher PFAS concentrations at age five were associated with substantially lower antibody concentrations against tetanus and diphtheria vaccines, with some children falling below the protective threshold. This was the first major study to directly link PFAS exposure to measurable immune system impairment in children.
Grandjean et al., Environmental Health Perspectives, 2017. Follow-up of the same Faroe Islands cohort at age 13. The inverse association between PFAS exposure and vaccine antibody concentrations persisted into adolescence, confirming that the immune suppression effects are not temporary.
Grandjean et al., Journal of Immunotoxicology, 2017. Demonstrated that PFAS exposure during infancy, including through breastfeeding, predicts lower vaccine antibody concentrations at age five. This established that the window of greatest vulnerability begins before birth and continues through early childhood.
Grandjean and Landrigan, The Lancet Neurology, 2006 and 2014. Two landmark reviews identifying industrial chemicals including lead, mercury, arsenic, PCBs and fluoride as developmental neurotoxicants. The 2014 update added six new chemicals to the list of confirmed developmental neurotoxicants and identified a further 200 chemicals as suspected. These papers established the scientific framework for understanding how chemical exposure during brain development causes permanent cognitive harm.
Timmermann, Grandjean et al., Environmental Research, 2024. Extended the vaccine immune suppression findings to adults and to COVID-19 mRNA vaccination. Danish adults with higher PFAS blood concentrations mounted a weaker antibody response to COVID-19 vaccination. The research suggests PFAS immune suppression is not limited to childhood or to traditional vaccines.
What He Has Said Publicly
The continued request for proof of harm leads to inaction. The research we have done should already trigger an effort to remove PFAS. They should, in my mind, be a matter of history.
Dr Philippe Grandjean, NIEHS Environmental Factor, October 2023
Children who had a doubled exposure to PFAS were only able to produce half as much of the antibody response to vaccines. This is not a subtle effect. This is a major finding with direct public health implications.
Dr Philippe Grandjean, KU Leuven Honorary Doctorate address, 2024
We have focused mainly on two PFAS compounds, but there are probably thousands of similar chemicals that rely on the same carbon-fluorine bond that is almost impossible to break down. It is this bond that offers what appear to be very useful properties, but at the same time results in adverse effects for the environment and human health.
Dr Philippe Grandjean, KU Leuven, 2024
Why This Research Matters
The implications of Grandjean's findings extend well beyond the specific studies themselves. If PFAS suppresses the immune response to vaccination, it raises questions about the broader effectiveness of vaccination programmes in populations with high PFAS exposure. It also suggests that PFAS-related immune suppression may affect the body's response to infection generally, not just to vaccines.
PFAS are among the most widespread environmental contaminants on earth. The UK Government's own February 2026 PFAS Plan confirmed contamination in 88% of surface water samples tested across England. These are not chemicals affecting a small exposed community. They are chemicals present in the bodies of virtually everyone alive today.
Grandjean's research is also notable for what it says about the regulatory framework. His studies were published in JAMA in 2012. The UK and EU did not begin moving toward binding limits on PFAS in drinking water until more than a decade later. His phrase about the continued request for proof of harm leading to inaction is not an abstract complaint. It is a description of what happened.
Grandjean's work sits at the intersection of two things that rarely appear together in public health research: rigorous long-term evidence and plain spoken urgency about what to do with it. He did not wait for consensus to form before saying what the data showed.
The evidence was already there. It still is.
Sources: Grandjean P et al., JAMA (2012) | Grandjean P et al., Environmental Health Perspectives (2017) | Grandjean P et al., Journal of Immunotoxicology (2017) | Grandjean P and Landrigan PJ, The Lancet Neurology (2006, 2014) | Timmermann A, Grandjean P et al., Environmental Research (2024) | NIEHS Environmental Factor, October 2023 | KU Leuven Honorary Doctorate address (2024)