Parabens as chemicals of emerging concern in the environment and humans: A review

Effects of exposure to single and multiple parabens on asthma development in an experimental mouse model and a prospective cohort study

Parabens are widely used preservatives present in consumer products like cosmetics and food. Although several epidemiological studies suggest that early-life exposure to parabens might alter the immune response and allergy risk in childhood, the evidence with respect to asthma is not clear. Therefore, we investigated the effect of paraben exposure on asthma development in mice and humans. Using a murine asthma model the experimental data show both, an asthma-reducing effect after direct exposure of adult mice to n-butyl paraben (nBuP) as well as an asthma-promoting effect after maternal exposure to ethyl paraben (EtP) in the female offspring. Interestingly, exposure of mice to a mixture of EtP and nBuP starting prenatally until the end of asthma induction in the adult offspring was without effect on allergic airway inflammation. In addition, parabens were determined within the German prospective mother-child cohort LINA and their single and mixture effect on asthma development in children within the first 10 years of life was estimated by logistic and Bayesian kernel machine regression (BKMR). Both approaches revealed no adverse effects of parabens on children's asthma development, neither when stratified for being at risk due to a positive family history of atopy nor when analysed separately for sex specificity. Therefore, we conclude that although single parabens might differentially impact asthma development, an adverse effect could not be seen in a multiple paraben exposure setting. Consequently, not only the time point of exposure but also multiple exposure scenarios to parabens should be considered in the evaluation of individuals' specific disease risk.

Occurrence and human exposure assessment of parabens in water sources in Osun State, Nigeria

Parabens are chemicals extensively used in pharmaceuticals, cosmetics, personal hygiene and food products as preservatives. They are classified as emerging contaminants with endocrine-disrupting capability. In this study, the concentrations of Methylparaben (MeP), Ethylparaben (EtP), Propylparaben (PrP) and Butylparaben (BuP) were obtained from groundwater, surface-water and packaged water samples collected from urban and rural areas of Osun State, Nigeria using HPLC-UV equipment. Data obtained were subjected to descriptive (Mean ± SD), inferential (Kruskal-Wallis test) and multivariate analyses. MeP had the highest average concentration of 163 and 68 μg L^-1 in surface water and groundwater respectively while concentrations of MeP, EtP, PrP and BuP were higher than previously reported in other countries. Methylparaben had the highest detection frequencies (88.0 and 50.0%) followed by BuP (69.0 and 50.0%) in surface water and groundwater respectively. No significant difference was observed for concentrations of parabens in groundwater samples in urban and rural sampling sites, suggesting that people living around these sites are equally exposed to any health implications from the use of paraben-polluted potable water. Principal Component Analysis (PCA) data suggest that the pairs MeP & EtP, PrP & BuP (in surface water samples) and MeP, EtP, & PrP (in groundwater samples) are from similar pollution sources. Ecological risk assessment using Algae, Fish, and Daphnia suggests Daphnia as the most sensitive organism while BuP and PrP show the highest health risk. Human exposure assessment showed that higher overall median estimated daily intake (EDI) values for groundwater were observed in infants (1.71 μg kg^-1 bw day^-1, ∑PBs) compared to toddlers (1.03 μg kg^-1 bw day^-1, ∑PBs), children (0.64 μg kg^-1 bw day^-1, ∑PBs), teenagers (0.51 μg kg^-1 bw day^-1, ∑PBs) and adults (0.62 μg kg^-1 bw day^-1, ∑PBs). Although these values are below limits set in a few countries, potential bioaccumulation could lead to severe health consequences.

Enhanced photocatalytic degradation of paraben preservative over designed g-C3N4/BiVO4 S-scheme system and toxicity assessment

Paraben preservatives have been listed as emerging pollutants due to their ubiquity in various environmental matrices, especially the water bodies. How to efficiently and practically eliminate these paraben pollutants is therefore of great importance. Herein, a designed S-scheme heterojunction photocatalyst, consisting of graphitic carbon nitride (g-C₃N₄) and monoclinic bismuth vanadate (BiVO₄), was fabricated by a facile hydrothermal synthesis and employed to treat benzyl-paraben (BzP). TEM and XPS analysis testified the intimate interaction between g-C₃N₄ and BiVO₄, and the consequently smoothed interfacial charge transfer rendered the feasible recombination of the photoexcited electrons (from BiVO₄) and holes (from g-C₃N₄). The as-established S-scheme system enabled the left g-C₃N₄ electrons and BiVO₄ holes to maintain the high redox abilities and accelerated the charge separation concurrently. In particular, the g-C₃N₄/BiVO₄ composite generated much higher photocurrent response as compared with pure g-C₃N₄ and BiVO₄, highlighting the improved separation of photoinduced charges. Therefore, under visible light and natural solar light irradiation, the g-C₃N₄/BiVO₄ composite showed the significantly enhanced photocatalytic degradation of BzP, which was further optimized with 5 wt% g-C₃N₄ in the composite. According to the Mott-Schottky plots and identified active species, the mechanism of the g-C₃N₄/BiVO₄ S-scheme heterojunction system was illustrated. In addition, during the photocatalytic degradation process, the acute toxicity of the reaction solutions on zebrafish embryos was notably reduced. In conclusion, the demonstrated strategy to enhance the photocatalytic performance by designing S-scheme heterostructure may provide more insights into the development of high-efficiency photocatalyst towards the solar energy utilization and environmental treatment. Furthermore, photocatalytic degradation had been proved to be an efficient method for eliminating the ecological risk of paraben pollutants, warranting more attention in future work.

Assessment of Thyroid Endocrine Disruption Effects of Parabens Using In Vivo, In Vitro, and In Silico Approaches

The extensive applications of parabens in foods, drugs, and cosmetics cause inevitable exposure to humans. Revealing the developmental toxicity of parabens is of utmost importance regarding their safety evaluation. In this study, the effects of four commonly used parabens, including methyl paraben (20 ∼ 200 μM), ethyl paraben (20 ∼ 100 μM), propyl paraben (5 ∼ 20 μM), and butyl paraben (BuP, 2 ∼ 10 μM), were investigated on the early development of zebrafish embryos and larvae. The underlying mechanisms were explored from the aspect of their disturbance in the thyroid endocrine system using in vivo, in vitro, and in silico assays. Paraben exposure caused deleterious effects on the early development of zebrafish, with BuP displaying the highest toxicity among all, resulting in the exposure concentration-related mortality, decreased hatching rate, reduced body length, lowered heart rate, and the incidence of malformation. Further investigation showed that paraben exposure reduced thyroid hormone levels and disturbed the transcriptional expressions of the target genes in the hypothalamic-pituitary-thyroid axis. Molecular docking analysis combined with in vitro GH3 cell proliferation assay testified that all test parabens exhibited thyroid receptor agonistic activities. The findings confirmed the developmental toxicity of the test parabens and their thyroid endocrine disruption effects, providing substantial evidence on the safety control of paraben-based preservatives.

Toxicity and removal of parabens from water: A critical review

Parabens are biocides used as preservatives in food, cosmetics and pharmaceuticals. They possess antibacterial and antifungal activity due to their ability to disrupt cell membrane and intracellular proteins, and cause changes in enzymatic activity of microbial cells. Water, one of our most valuable natural resource, has become a huge reservoir for parabens. Halogenated parabens from chlorination/ozonation of water contaminated with parabens have shown to be even more persistent in water than other types of parabens. Unfortunately, there is dearth of data on their (halogenated parabens) presence and fate in groundwater which serves as a major source of drinking water for a huge population in developing countries. An attempt to neglect the presence of parabens in water will expose man to it through ingestion of contaminated food and water. Although there are reviews on the occurrence, fate and behaviour of parabens in the environment, they largely omit toxicity and removal aspects. This review therefore, presents recent reports on the acute and chronic toxicity of parabens, their estrogenic agonistic and antagonistic activity and also their relationship with antimicrobial resistance. This article further X-rays several techniques that have been employed for the removal of parabens in water and their drawbacks including adsorption, biodegradation, membrane technology and advanced oxidation processes (AOPs). The heterogeneous photocatalytic process (one of the AOPs) appears to be more favoured for removal of parabens due to its ability to mineralize parabens in water. However, more work is needed to improve this ability of heterogeneous photocatalysts. Perspectives that will be relevant for future scientific studies and which will drive policy shift towards the presence of parabens in our drinking waters are also offered. It is hoped that this review will elicit some spontaneous actions from water professionals, scientists and policy makers alike that will provide more data, effective technologies, and adaptive policies that will address the growing threat of the presence of parabens in our environment with respect to human health.