Substances of unknown or variable composition, complex reaction products, and biological materials (UVCBs) are commonly found in the environment. However, assessing their human toxicological risk is challenging due to their variable composition and many constituents. Metal naphthenate salts are one such category of UVCBs that are the reaction products of naphthenic acids with metals to form complex mixtures. Metal naphthenates are often found or used in household and industrial materials with potential for human exposure, but very few of these materials have been evaluated for causing human health hazards. Herein, we evaluate metal naphthenates using predictions derived from read-across and quantitative structure-activity/property relationship (QSAR/QSPR) models. Accordingly, we first built a computational chemistry library by enumerating the structures of naphthenic acids and derived 11,850 QSAR-acceptable structures; then, we used open and commercial in silico tools on these structures to predict a set of physicochemical properties and toxicity endpoints. We then compared the QSAR/QSPR predictions with available experimental data on naphthenic acids to provide a more complete picture of the contributions of the components to the toxicity profiles of metal naphthenate mixtures. The available systematic acute oral toxicity values (LD(50)) and QSAR LD(50) predictions of all the naphthenic acid components indicated low concern for toxicity. The point of departure predictions for chronic repeated dose toxicity for the naphthenic acid components using QSAR models developed from studies on rats ranged from 25 to 50 mg/kg/day. These values are in good agreement with findings from studies on copper and zinc naphthenates, which had no observed adverse effect levels of 30 and 118 mg/kg/day, respectively. Hence, this study demonstrates how published in silico approaches can be used to identify the potential components of metal naphthenates for further testing, inform groupings of UVCBs such as naphthenates, as well as fill the data gaps using read-across and QSAR models to inform risk assessment.

Two siblings aged 5 and 15 years from Connecticut were hospitalized with petechial rash, oral mucositis, and severe thrombocytopenia approximately 10 days after they played with a jar of elemental mercury they found in their home. Before the mercury exposure was disclosed, the siblings were treated with platelet transfusions, intravenous immune globulin (IVIG) for possible immune thrombocytopenic purpura, and antibiotics for possible infectious causes. When their conditions did not improve after 6 days, poison control facilitated further questioning about toxic exposures including mercury, testing for mercury, and chelation with dimercaptosuccinic acid. The older sibling soon recovered, but the younger child required a prolonged hospitalization for severe thrombocytopenia, ultimately receiving repeated doses of IVIG, steroids, and romiplostim, a thrombopoietin receptor agonist. Close collaboration among multiple agencies was required to identify the extent of mercury contamination, evaluate and treat the other family members, and decontaminate the home. These cases demonstrate the importance of ongoing public health outreach to promote early detection of elemental mercury toxicity, and the need to evaluate for environmental exposures when multiple close contacts experience similar signs and symptoms.

What would you want to know before your children attend a day care opening in a former industrial building or adjacent to a nail salon? Are children at risk if their new preschool is located on former farmland where lead arsenate pesticide might have been used? What site-related environmental risks are most concerning for children attending early care and education (ECE) facilities? | | States involved with the Agency for Toxic Substances and Disease Registry’s (ATSDR) Choose Safe Places for Early Care and Education (CSPECE) effort are addressing site-related questions like these to help protect children from harmful environmental exposures.

Licensed child care centers are generally considered to be safe because they are required to meet state licensing regulations. As part of their licensing requirements, many states inspect child care centers and include an assessment of the health and safety of the facility to look for hazardous conditions or practices that may harm children. However, most states do not require an environmental assessment of the child care center building or land to prevent a center from being placed on, next to, or inside contaminated buildings. Having worked on several sites where child care centers were affected by environmental contaminants, the Centers for Disease Control and Prevention and the Agency for Toxic Substances and Disease Registry (ATSDR) endeavor to raise awareness of this issue. One of ATSDR's partner states, Connecticut, took a proactive, non-regulatory approach to the issue with the development its Child Day Care Screening Assessment for Environmental Risk Program.