As for the growing concern about the effects of exposure to potentially toxic substances on the health of fetuses and infants, researchers report the finding of several endocrine disruptors in Danish infants in a recent study. Environment International log study. More specifically, this study found that breastfeeding is associated with a higher concentration of some of these chemicals or their metabolites in infants compared to infants fed a mixed diet.
Study: Benzophenones, bisphenols and other polychloro/phenolic substances in Danish infants and their parents – including longitudinal assessments before and after introduction to mixed diet. Image Credit: Prostock Studio / Shutterstock.com
Bisphenols and benzophenones (BPs) are two examples of phenolic and polychlorinated substances to which people are exposed in their environment. These chemicals are often used in the production of consumer products; thus they are considered ubiquitous.
For example, BPs filter ultraviolet (UV) rays in various consumer products, including skin creams or curtains with UV-shielding properties. In addition, bisphenols, including the much-studied bisphenol A (BPA), one of the most abundantly produced chemicals in the world, are used to produce epoxy resins and polycarbonates in consumer products and during recycling.
Triclosan and triclocarban are antibacterial agents used in personal care products and cleaning/disinfection products. Chlorophenols can be incorporated into pesticides and herbicides, with 2,5-dichlorophenol (2,5-DCP) also being used as a disinfectant.
Phenylphenols are fungicides and are often used post-harvest to prevent fungal growth in fruit orchards. These chemicals can also be used for industrial or household disinfection.
Most of these chemicals undergo rapid degradation and are eliminated in the urine and/or faeces, indicating that they are not persistent. However, some chemicals exhibit pseudo-persistence, allowing them to remain in the body almost forever as a result of repeated or constant ingestion, skin contact, or inhalation. This continuous exposure is being investigated for its potential for endocrine disruption.
In Denmark, most young men are still exposed to most of these chemicals, despite current efforts to reduce their use. BPA substitutes such as bisphenol S (BPS) and bisphenol F (BPF) are produced in greater quantities and as a result have become more widely used in Europe and the United States over the past decade.
The current human biomonitoring study aimed to monitor the measurements of these substances in the urine and serum of parents and infants during breastfeeding and mixed feeding.
Called TRIO, this study involved an analysis of the urine samples of more than a hundred babies and their parents. Paired samples from approximately 60 infants from the FOOD study during the exclusively breastfed period and after exposure to a mixed diet were also included.
Of the 22 substances measured in the urine, 12 were present in more than 50% of the samples from parents and infants. The concentrations of excreted substances varied considerably between samples.
In the TRIO study, BP-3 was present in almost all samples from infants and parents. In addition, BPA, BPS, triclosan and 2,4-DCP were identified in more than 75% of the parental samples and, with the exception of 2,4-DCP, almost 95% of the infant samples. BP-1 was also commonly observed in all samples.
Urine samples from fathers had significantly higher urine concentrations of these substances compared to those from mothers. However, this difference disappeared when estimated daily urinary excretion (DUE) values were used.
Infants had DUE values for BP, 4-hydroxy-benzophenone (4-BHP), BPA, BPS, triclosan, and 2-phenylphenol that were much higher than their parents’. The highest levels of BP-3 were identified in some infant samples, with some patient samples being 20 and 40 times the peak value in fathers and mothers, respectively.
The concentrations of triclosan, as well as BP-1 and BP-3, were highly correlated, suggesting that they all came from the same domestic sources. Levels of these compounds in infants and their mothers were also well correlated, as were 4-BHP and BPA levels.
A greater variation was observed for the levels of these connections between families compared to within families, where parents showed a good mutual correlation. Apart from these substances, others showed similar increases or decreases in correlation.
For example, simultaneous exposure to several substances may have occurred within some families. In particular, certain compounds, such as BP-1 and 4-HBP, are by-products of the metabolism of BP and BP-3 and compounds that are used for their own properties.
In the FOOD study, seven substances, including BP, BP-1, BP-3, 4-HBP, BPA and BPS, were present in more than 50% of urine samples in both groups. The excretion profile changed with the analysis method; however, some were higher in infants compared to their parents.
After adjusting for osmolality, BP-1, BPA, BPS and 2,4-DCP were lower; However, 4-BHP was higher in exclusively breastfed infants.
After adjusting for body weight, exclusively breastfed infants excreted 4-BHP and triclosan in higher concentrations than when introduced with other foods. This could be due to inhaling chemicals from personal care products or cleaning products, even when used by their parents. Breast milk could be another source of these substances.
In the mixed diet group, 2,4-DCP, 2-PP and 2,5-DCP were detected more frequently. This is probably because many of these are pesticides used in growing grains, fruits and vegetables, all of which form the basis of solid foods.
The mean age of infants in the exclusive breastfeeding cohort was two weeks old, compared to 30 weeks in the mixed diet cohort. Therefore, the duration of exposure should be taken into account when assessing the urinary excretion profile.
No correlations were found between the two groups for any substance, with the intra-individual variation being much larger than the inter-individual differences.
Low levels of chemicals have been found to be excreted in the urine of both babies and parents; however, the presence of different endocrine disruptors in the same samples indicates the potential for additive effects with each other, as well as with other substances in the diet or the environment in general. Most of this exposure came from household chemicals and personal care products for parents or babies.
In general, parental exposure reflected infant exposure, although levels varied significantly between adults and infants within families. Higher mean levels have been found in pregnant women and preconception in several studies conducted in France, the US and Puerto Rico. This may be due to the deliberate phasing out of these connections in Denmark in recent years.
Interestingly, triclosan detection rates were high; however, this substance is only allowed in a very small group of personal care products in Denmark and in a very low concentration.
The current study also demonstrates the importance of using estimated DUEs to obtain more accurate values reflecting actual exposure. This method helped demonstrate the similar or higher infant exposure rates to several of these substances during exclusive breastfeeding compared to the introduction of other foods.
- Frederikson, H., Ljubcic, M.L., Upners, EN, et al. (2022). Benzophenones, bisphenols and other polychloro/phenolic substances in Danish infants and their parents – including longitudinal assessments before and after introduction to mixed diet. Environment International. doi:10.1016/j.envint.2022.107532.