On November 2, 2020, a study led by Courtney M. Gardner from Duke University was published in peer-reviewed journal Environmental Science and Technology Letters that discovered changes in the gut microbiome of children associated with increased accumulation of semi-volatile organic chemicals (SVOCs), which could potentially reduce overall human health and cause an imbalance of bacteria in the gut.
SVOCs are commonly found in indoor environments and can be taken up through inhalation, dust, and contact with surfaces of everyday products. The chemical group of SVOCs includes, among others, flame retardants (e.g. polybrominated diphenyl ethers) and plasticizers (e.g. phthalates). A previous study has postulated that chemicals migrating from food contact materials (FCMs), including SVOCs, may negatively affect human gut health (FPF reported). However, research that investigates the effects on children who are especially vulnerable to chemical exposures and still have immature gut microbiota is scarce.
The goal of the presented study was to assess how exposure to SVOCs is associated with changes in the gut microbiome composition of young children. To answer this question, the researchers collected blood, urine, and fecal samples from 79 children (between the ages of 3 and 6) and tested for 44 SVOCs as well as analyzed the correlated presence of bacteria and fungi species.
In total, 43 of 44 SVOC biomarkers were detected in blood or urine samples, with 29 compounds detected in >95% of children. The researchers found, among others, phthalates and phthalate replacements including monoethyl phthalate (MEP; CAS 2306-33-4) and mono benzyl phthalate (MBzP; CAS 2528-16-7), phenols such as benzophenone-3 (BP-3; CAS 131-57-7 ), and per- and polyfluoroalkyl substances (PFAS) such as perfluorooctanesulfonic acid (PFOS; CAS 1763-23-1).
The researchers found that the presence of SVOCs affected the majority of gut microorganisms. Especially PFOS was associated with a decline of less abundant but equally important species for assimilation of nutrients, e.g. Thermogemmatisporales, Stigonematales, and Legionellales. For fungi, it was observed that certain chemicals, particularly phthalates, parabens, and flame retardants, were strongly correlated with decreased occurrence of less abundant species.
The researchers hypothesize these less common, but equally beneficial, species are more sensitive to the chemicals and are therefore replaced by the more dominant strains.
The researchers also observed an increased abundance of dehalogenating bacteria e.g. Dehalobacterium spp. in children with higher SVOC exposure and particularly associated with the presence of halogenated compounds and antimicrobials, e.g. 2,4-Dichlorophenol (2,4-DCP; CAS 120-83-2), bis (1,3-dichloropropyl) phosphate (BDCPP; CAS 68460-03-7), and triclosan (CAS 3380-34-5). A previous study by Michalovich et al. in Nature Communications described that the presence of Moraxella spp. and Dehalobacterium spp. in the human gut microbiome may be associated with adverse health conditions (e.g. asthma) in adults. However, it is still unclear if and how these organisms influence the health conditions in adults or long-term effects in young children.
The authors concluded that further research is needed to verify the observed links, their corresponding influence on the health status of maturing children, and the role of confounding factors. This could be achieved with a larger group of participants, extensive diet analysis, and continuous or repeated measures, e.g. following particular individuals over prolonged periods of time.
The authors write in their article that “while these data do not denote causation, they offer an indication of taxa that may be impacted by exposure to SVOCs and provide a springboard for future research. Gaining a more holistic understanding of the interactions among anthropogenic chemicals, the gut microbiome, and human health is a critical step in advancing public health.”
Gardener et al (November 2, 2020). “Exposures to Semivolatile Organic Compounds in Indoor Environments and Associations with the Gut Microbiomes of Children.” Environmental Science Technology Letters
Hoffman et al. (October 2018). «Biomarkers of Exposure to SVOCs in Children and their Demographic Associations: The TESIE Study.” Environment International
Chui et al. (May 11, 2020). “Contemporary Review: The Impact of Environmental Chemicals on the Gut Microbiome.” Toxicological Sciences
Michalovich et al. (December 2019). “Obesity and disease severity magnify disturbed microbiome-immune interactions in asthma patients.” Nature Communications
Lai et al. (October 2018). “Dietary exposure to the environmental chemical, PFOS on the diversity of gut microbiota, associated with the development of metabolic syndrome.” Frontiers