Study: Benzophenones, bisphenols and other polychlorinated/phenolic substances in Danish infants and their parents - including longitudinal assessments before and after introduction to mixed diet. Image Credit: Prostock-studio / Shutterstock.com

Endocrine-disrupting chemicals found in the urine of Danish infants

Regarding concerns about the effects of exposure to potentially toxic substances on fetal and infant health, researchers report in a recent Environment International magazine studies. More specifically, this study found that breastfeeding is associated with higher concentrations of some of these chemicals or their metabolites in infants compared to formula-fed infants.

Studies: Benzophenones, bisphenols and other polychlorinated/phenolic substances in Danish infants and their parents – including long-term assessments before and after the introduction of mixed diets. Image credit: Prostock-studio / Shutterstock.com

Introduction

Bisphenols and benzophenones (BPs) are two examples of phenolic and polychlorinated substances that humans are exposed to in their environment. These chemicals are commonly used in the manufacture 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 shading properties. In addition, bisphenols, including the widely studied bisphenol A (BPA), one of the most abundantly produced chemicals in the world, are used to make epoxy resins and polycarbonates in consumer products and in recycling.

Triclosan and triclocarban are antibacterial agents used in personal care products and cleaning/disinfectants. Chlorophenols can be incorporated into pesticides and herbicides, with 2,5-dichlorophenol (2,5-DCP) also used as a disinfectant.

Phenylphenols are fungicidal agents and are often used post-harvest to prevent fungal growth in orchards. These chemicals can also be used for industrial or domestic disinfection.

Most of these chemicals undergo rapid degradation and are excreted in urine and/or feces, indicating that they are not persistent. However, some chemicals exhibit pseudo-persistence, which allows them to remain present in the body for almost all time as a result of repeated or continuous 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 being produced in more significant quantities and, as a result, have been used on a larger scale in Europe and the United States over the past decade.

The current human biomonitoring study was conducted to monitor measurements of these substances in the urine and serum of parents and infants during periods of breastfeeding and mixed feeding.

The study, called TRIO, involved the analysis of urine samples from more than a hundred infants and their parents. Paired samples from about 60 infants from the FOOD study during the period when they were exclusively breastfed and after being exposed to a mixed diet were also included.

Study results

Of the 22 substances measured in urine, 12 were present in more than 50% of samples from parents and infants. Concentrations of excreted substances varied significantly 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 parental samples and, except for 2,4-DCP, in almost 95% of infant samples. BP-1 was also commonly observed in all samples.

Fathers’ urine samples had significantly higher urinary concentrations of these substances compared to those obtained from mothers. However, this difference disappeared when estimated daily urinary excretion (DUE) values ​​were used.

The infants had DUEs 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 reaching 20 and 40 times higher than the maximal value in fathers and mothers, respectively.

Concentrations of triclosan, as well as BP-1 and BP-3, were highly correlated, suggesting that they all originated from the same domestic sources. Levels of these compounds in infants and their mothers were also well correlated, as were levels of 4-BHP and BPA.

Greater differences in the levels of these compounds were observed between families compared to families where the parents showed a good correlation with each other. Other than these substances, others showed similar increases or decreases in correlation.

In some families, there may have been simultaneous exposure to several substances. In particular, certain compounds such as BP-1 and 4-HBP are by-products of BP and BP-3 metabolism 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 method of analysis; 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 at higher concentrations than when fed other foods. It could be caused by inhaling chemicals from personal care products or cleaning products, even those used by their parents. Another source of these substances could be breast milk.

2,4-DCP, 2-PP and 2,5-DCP were more frequently detected in the mixed diet group. This is probably because many of them are pesticides used in the cultivation of grains, fruits and vegetables, all of which form the basis of solid foods.

The average age of infants in the exclusively breastfed group was two weeks compared to 30 weeks in the mixed feeding group. Therefore, the duration of exposure should be taken into account when assessing the urinary excretion profile.

No correlations were found for any substance between the two groups, with intraindividual variation being much higher than interindividual differences.

Impacts

Low levels of the chemicals were found to be excreted in the urine of both infants and parents; however, the presence of multiple endocrine-disrupting chemicals in the same samples suggests the potential for additive effects with each other, as well as with other substances in the diet or in the environment in general. Most of this exposure came from household chemicals and personal care products for parents or children.

Overall, parental exposure mirrored infant exposure, although levels varied significantly between adults and infants within families. Higher mean levels were found in pregnant women and preconception in several studies conducted in France, the US and Puerto Rico. This could be due to the deliberate phase-out of these compounds during the last few years in Denmark.

Interestingly, the detection rate of triclosan was high; however, this substance is allowed in Denmark only in a very small group of personal care products and in a very low concentration.

The current study also establishes the importance of using estimated DUEs to obtain more accurate values ​​that reflect actual exposures. This method helped demonstrate similar or higher levels of infant exposure to some of these substances during exclusive breastfeeding compared to the introduction of other foods.

Link to journal:

  • Frederikson, H., Ljubcic, ML, Upners, EN, et al. (2022). Benzophenones, bisphenols and other polychlorinated/phenolic substances in Danish infants and their parents – including long-term assessments before and after the introduction of mixed diets. Environment International. doi:10.1016/j.envint.2022.107532.

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