Quantitative Risk Assessment of Dermal Sensitization Potential Following Use of Shampoo Products Containing the Formaldehyde Releasing Preservative DMDM Hydantoin.

Historically, formaldehyde was used as a preservative in personal care products to extend product shelf-life; however, given its skin sensitization potential it has been phased out of use and replaced with formaldehyde-releasing preservatives, such as Dimethyloldimethyl hydantoin (DMDMH). A relationship has been established between positive patch test results following exposure to DMDMH and previous sensitization to formaldehyde. Upon direct contact with the skin, formaldehyde can react with skin proteins and cause an acute inflammatory reaction, which may progress to skin sensitization following repeated exposure. This quantitative risk assessment (QRA) aimed to assess the risk of skin sensitization induction following use of shampoo products containing the maximum allowable concentrations of DMDMH in formulation (1% w/v), translating to a free formaldehyde concentration of 0.02%. To determine a margin of safety (MOS) for exposure to DMDMH from use of shampoo products, consumer exposure levels (CEL) were estimated based on typical use scenarios and then benchmarked against an acceptable exposure level (AEL). The AEL was derived using a weight of evidence approach where a range of no expected sensitization induction levels (NESILs) was utilized. The MOS values for a shampoo product containing 1% DMDMH (.02% formaldehyde) was above 1 for the typical use scenario indicating a low likelihood of skin sensitization induction among healthy individuals. Thus, it can be concluded that shampoo products containing DMDMH at or below current allowable concentrations are not expected to increase the risk of skin sensitization induction.

Hair dye and risk of skin sensitization induction: a product survey and quantitative risk assessment for para-phenylenediamine (PPD).

BACKGROUND: Para-Phenylenediamine (PPD) is a commonly used dye intermediate in permanent hair dye formulations, and exposure to PPD has been associated with allergic contact dermatitis at certain doses. PURPOSE: Determine the concentration of PPD in a survey of self-application permanent hair dye products, and perform a quantitative risk assessment to determine the risk of skin sensitization induction following application of these products. METHODS: Consumer exposure levels (CELs) to PPD following application of hair dye products were estimated using the maximum amount of hair dye that can adhere to the surface area of the scalp, the measured concentration of PPD in the hair dye product, a retention factor, the dermal absorption of PPD, and the surface area of the scalp. CELs were calculated for various exposure scenarios, and were stratified by hair dye shade. RESULTS: All estimated CELs did not exceed the acceptable exposure level. Specifically, margins of safety ranged from 2.3 to 1534 for black dyes, 2.9 to 5031 for brown dyes, and 26 to 5031 for blonde dyes. CONCLUSIONS: Findings suggest that use of the evaluated permanent hair dyes, under the evaluated exposure scenarios, would not be expected to induce skin sensitization due to PPD exposure at concentrations ≤0.67%.

Current approaches for safer design of engineered nanomaterials.

The surge of applications for engineered nanomaterials (ENMs) across multiple industries raises safety concerns regarding human health and environmental impacts. ENMs can be hazardous through various mechanisms, including, particle dissolution and shedding of toxic metal ions, surface reactivity and perturbation of cellular membranes, lysosomal membrane damage, activation of inflammation pathways (e.g., NLRP3 inflammasome), etc. The aim of this review is therefore to discuss practical approaches for the safer design of ENMs through modification of their physicochemical properties that can lead to acute and/or chronic toxicity. This is premised on our understanding of how different ENMs induce toxicity within various biological systems. We will summarize studies that have investigated nanomaterial toxicity both in vitro and in vivo to understand the underlying mechanisms by which nanoparticles can cause inflammation, fibrosis, and cell death. With this knowledge, researchers have identified several design strategies to counter these mechanisms of toxicity. In particular, we will discuss how metal doping, surface coating and covalent functionalization, and adjustment of surface oxidation state and aspect ratio of ENMs could reduce their potential adverse effects. While these strategies might be effective under certain experimental and exposure scenarios, more research is required to fully apply this knowledge in real life applications of nanomaterials.

Local adaptation to osmotic environment in killifish, Fundulus heteroclitus, is supported by divergence in swimming performance but not by differences in excess post-exercise oxygen consumption or aerobic scope.

Regulation of internal ion homeostasis is essential for fishes inhabiting environments where salinities differ from their internal concentrations. It is hypothesized that selection will reduce energetic costs of osmoregulation in a population's native osmotic habitat, producing patterns of local adaptation. Killifish, Fundulus heteroclitus, occupy estuarine habitats where salinities range from fresh to seawater. Populations inhabiting an environmental salinity gradient differ in physiological traits associated with acclimation to acute salinity stress, consistent with local adaptation. Similarly, metabolic rates differ in populations adapted to different temperatures, but have not been studied in regard to salinity. We investigated evidence for local adaptation between populations of killifish native to fresh and brackish water habitats. Aerobic scope (the difference between minimum and maximum metabolic rates), excess post-exercise oxygen consumption, and swimming performance (time and distance to reach exhaustion) were used as proxies for fitness in fresh and brackish water treatments. Swimming performance results supported local adaptation; fish native to brackish water habitats performed significantly better than freshwater-native fish at high salinity while low salinity performance was similar between populations. However, results from metabolic measures did not support this conclusion; both populations showed an increase in resting metabolic rate and a decrease of aerobic scope in fresh water. Similarly, excess post-exercise oxygen consumption was higher for both populations in fresh than in brackish water. While swimming results suggest that environmentally dependent performance differences may be a result of selection in divergent osmotic environments, the differences between populations are not coupled with divergence in metabolic performance.

Evaluation of chemicals leached from PET and recycled PET containers into beverages.

The use of recycled polyethylene terephthalate (rPET) containers, a recent shift in the beverage industry, poses new potential human health concerns including contamination from the original container; use of additives, detergents, and catalysts during recycling; and improper recycling practices. The purpose of this analysis was to evaluate available data regarding: (1) chemicals leached from PET and rPET in bottle form; (2) concentration of these chemicals; and (3) trends between rPET percent and concentration of chemicals leached. This analysis identified 211 scientific articles related to recycled plastic and leachables. Three articles met the inclusion criteria: (1) plastic was in bottle form; (2) plastic was made of PET or rPET; and (3) the study analyzed both PET and rPET using the same methods. This evaluation demonstrated that only nine compounds - benzene, styrene, acetaldehyde, 2-methyl-1,3-dioxolane, furan, bisphenol A (BPA), 2-buta-none, acetone, and limonene - have been studied. Notably, the leachable concentration of benzene, styrene, and BPA increased as the percent of recycled content increased from 0 to 100%. However, 2-methyl-1,3-dioxolane and furan implied a reverse trend, where the leachable concentration decreased as the percent of recycled content increased from 0 to 100%. The concentrations of 2-butanone, acetone, and limonene did not follow any suggested trend. Evidently, recycling PET can lead to changes in the leachables profile. This analysis further identified key areas of research, including testing a variety of liquid types, that need to be addressed to adequately conduct a human health risk assessment.