Addressing concerns about the effects of exposure to potentially toxic substances on fetal and infant health, researchers report the finding of several endocrine-disrupting chemicals in Danish infants in a recent study in the journal Environment International. 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 those fed a mixed diet.
Study: Benzophenones, bisphenols and other polychlorinated/phenolic substances in Danish infants and their parents, including longitudinal assessments before and after introduction to the mixed diet. Image credit: Prostock-studio / Shutterstock.com
Introduction
Bisphenols and benzophenones (BP) are two examples of phenolic and polychlorinated substances to which humans are exposed in their environment. These chemicals are commonly used in the manufacture of consumer products; therefore, they are considered ubiquitous.
BPs, for example, filter ultraviolet (UV) rays in various consumer products, including skin creams or curtains with UV protective properties. In addition, bisphenols, including the widely studied bisphenol A (BPA), one of the most abundant chemicals in the world, are used to make epoxy and polycarbonate resins in consumer products and during recycling.
Triclosan and triclocarban are antibacterial agents used in personal care and cleaning/disinfecting products. 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 fruit orchards. These chemicals can also be used for industrial or household disinfection.
Most of these chemicals undergo rapid degradation and are eliminated through urine and/or feces, thus indicating that they are not persistent. However, some chemicals exhibit pseudo-persistence, which allows them to remain present in the body almost all the time due to repeated or constant ingestion, skin contact, or inhalation. This continuous exposure is being investigated because of 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 larger quantities and, as a result, have been used on a larger scale in Europe and the United States over the past ten years.
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 breast-feeding and mixed-diet feeding.
This study, which was named TRIO, included an analysis of urine samples from more than one hundred babies and their parents. Paired samples of about 60 infants from the FOOD study during the period when they were exclusively breastfed and after exposure to a mixed diet were also included.
Results of the study
Of the 22 substances measured in urine, 12 were present in more than 50% of the parent and infant samples. The concentrations of excreted substances varied significantly between samples.
In the TRIO study, BP-3 was present in almost all infant and parent samples. In addition, BPA, BPS, triclosan, and 2,4-DCP were identified in more than 75% of parental samples and, except for 2,4-DCP, almost 95% of child 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 DUE values for BP, 4-hydroxy-benzophenone (4-BHP), BPA, BPS, triclosan, and 2-phenylphenol that were significantly higher than their parents. The highest levels of BP-3 were identified in some infant samples, with some patient samples reaching 20- and 40-fold higher than the peak value in mothers and fathers, respectively.
Triclosan concentrations, as well as BP-1 and BP-3, were highly correlated with each other, suggesting that they all originated from the same domestic sources. The levels of these compounds in the infants and their mothers were also well correlated, as were the levels of 4-BHP and BPA.
Between families, a greater variation in the levels of these compounds was observed compared to families, where parents showed a good correlation between them. Apart from these substances, others showed similar increases or decreases in the correlation.
Thus, simultaneous exposure to several substances may have occurred within some families. In particular, certain compounds, such as BP-1 and 4-HBP, are byproducts 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 the urine samples of both groups. The excretion profile changed with the analysis method; however, some were higher in infants compared to their parents.
After adjustment for osmolality, BP-1, BPA, BPS, and 2,4-DCP were lower; however, 4-BHP was higher in exclusively breastfed infants.
When adjusted for body weight, exclusively breastfed infants excreted 4-BHP and triclosan at higher concentrations than when fed other foods. This could be due to inhaling chemicals from personal care products or cleaning products, even those 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 likely because many of these are pesticides used in the cultivation of grains, fruits and vegetables, which form the basis of solid foods.
The average age of infants in the exclusively breastfed cohort was two weeks compared to 30 weeks in the mixed diet cohort. Therefore, the duration of exposure should be taken into account when evaluating the urinary excretion profile.
No correlations were found for any substance between the two groups, with intra-individual variation far exceeding inter-individual differences.
Implications
Low levels of the chemicals were found to be excreted in the urine of both the babies and the parents; however, the presence of multiple endocrine-disrupting chemicals 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 originated from household chemicals and personal care products for parents or babies.
In general, parental exposure mirrored child exposure, although levels varied significantly between adults and infants within families. Higher mean levels have been found in pregnant and preconception women in several studies in France, the US, and Puerto Rico. This could be due to the intentional disposal of these compounds in recent years in Denmark.
Interestingly, detection rates for triclosan 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 establishes the importance of using estimated DUEs to obtain more accurate values that reflect actual exposures. This method helped demonstrate similar or higher rates of infant exposure to several of these substances during exclusive breastfeeding compared to the introduction of other foods.
Journal reference:
- Frederikson, H., Ljubcic, ML, Upners, EN, et al. (2022). Benzophenones, bisphenols and other polychlorinated/phenolic substances in Danish infants and their parents, including longitudinal assessments before and after introduction to mixed diet. International Environment. doi:10.1016/j.envint.2022.107532.