Particle size distributions of lead measured in battery manufacturing and secondary smelter facilities and implications in setting workplace lead exposure limits

<p>Inhalation plays an important role in exposures to lead in airborne particulate matter in occupational settings, and particle size determines where and how much of airborne lead is deposited in the respiratory tract and how much is subsequently absorbed into the body. Although some occupational airborne lead particle size data have been published, limited information is available reflecting current workplace conditions in the U.S. To address this data gap, the Battery Council International (BCI) conducted workplace monitoring studies at nine lead acid battery manufacturing facilities (BMFs) and five secondary smelter facilities (SSFs) across the U.S. This article presents the results of the BCI studies focusing on the particle size distributions calculated from Personal Marple Impactor sampling data and particle deposition estimates in each of the three major respiratory tract regions derived using the Multiple-Path Particle Dosimetry model. The BCI data showed the presence of predominantly larger-sized particles in the work environments evaluated, with average mass median aerodynamic diameters (MMADs) ranging from 21–32 µm for the three BMF job categories and from 15–25 µm for the five SSF job categories tested. The BCI data also indicated that the percentage of lead mass measured at the sampled facilities in the submicron range (i.e., <1 µm, a particle size range associated with enhanced absorption of associated lead) was generally small. The estimated average percentages of lead mass in the submicron range for the tested job categories ranged from 0.8–3.3% at the BMFs and from 0.44–6.1% at the SSFs. Variability was observed in the particle size distributions across job categories and facilities, and sensitivity analyses were conducted to explore this variability. The BCI results were compared with results reported in the scientific literature. Screening-level analyses were also conducted to explore the overall degree of lead absorption potentially associated with the observed particle size distributions and to identify key issues associated with applying such data to set occupational exposure limits for lead.</p

Expanding the Toolbox: Hazard-Screening Methods and Tools for Identifying Safer Chemicals in Green Product Design

A key focus of green product design is to reduce the product’s inherent chemical hazard. Various alternative assessment methodologies may be used to compare the hazard properties of possible candidate chemicals. However, only a small fraction of the chemicals currently in commercial use are adequately characterized in terms of toxicological effects. This limitation can hamper the study of safer chemical alternatives and increase the likelihood of regrettable substitutions. Approaches for addressing such data gaps include read-across, <i>in silico</i> programs and high throughput <i>in chemico</i> and <i>in silico</i> assays. Each of these show considerable promise although a consensus on how to use them for hazard evaluation of data poor chemicals is lacking. The limitations of such tools, which attempt to simplify complex biology into key predictive factors, is also often underestimated. To evaluate currently available approaches for addressing data gaps, we established three test sets of chemicals, each with structural similarity to a target chemical (target chemical 1: 4-phenylenediamine, target chemical 2: hydroxyethyl acrylate, target chemical 3: methylisothiazolone). We first compared results from the <i>in silico</i> programs Toxtree and Derek Nexus with animal test data obtained using standard assays. We then compared chemical similarity scores calculated by two computational tools Toxmatch and ChemMine. Lastly, we refined our test sets by applying a series of exclusion criteria, including <i>in silico</i> analysis and physicochemical data relevant for skin sensitization (e.g., molecular weight, water solubility, and vapor pressure). The <i>in silico</i> programs in combination exhibited a sensitivity of 92% and specificity of 88%. Toxmatch and ChemMine demonstrated good agreement in their similarity score rankings across the three test sets (TS1: W = 0.74, p = 0.014; TS2: W = 0.72, p = 0.067; TS3: W = 0.87, p = 0.095). Narrowing our chemical test sets using physical chemical properties and <i>in silico</i> evaluation improved the overall accuracy of our read-across approach compared with the initial unrefined test sets (TS1: 56% improved to 100%; TS2: 54% to 100%; TS3: 50% to 100%). Our findings support the development of robust read-across approaches incorporating available data-gap filling tools to help conduct screening level alternatives assessments and identify safer chemicals as part of green product design

DataSheet1_Non-pyrogenicity and biocompatibility of parylene-coated magnetic bead implants.PDF

Clinical grade magnetic bead implants have important applications in interfacing with the human body, providing contactless mechanical attachment or wireless communication through human tissue. We recently developed a new strategy, magnetomicrometry, that uses magnetic bead implants as passive communication devices to wirelessly sense muscle tissue lengths. We manufactured clinical-grade magnetic bead implants and verified their biocompatibility via intramuscular implantation, cytotoxicity, sensitization, and intracutaneous irritation testing. In this work, we test the pyrogenicity of the magnetic bead implants via a lagomorph model, and we test the biocompatibility of the magnetic bead implants via a full chemical characterization and toxicological risk assessment. Further, we test the cleaning, sterilization, and dry time of the devices that are used to deploy these magnetic bead implants. We find that the magnetic bead implants are non-pyrogenic and biocompatible, with the insertion device determined to be safe to clean, sterilize, and dry in a healthcare setting. These results provide confidence for the safe use of these magnetic bead implants in humans.</p

Safer Formulation Concept for Flame-Generated Engineered Nanomaterials

The likely success or failure of the nanotechnology industry depends on the environmental health and safety of engineered nanomaterials (ENMs). While efforts toward engineering safer ENMs are sparse, such efforts are considered crucial to the sustainability of the nanotech industry. A promising approach in this regard is to coat potentially toxic nanomaterials with a biologically inert layer of amorphous SiO₂. Core–shell particles exhibit the surface properties of their amorphous SiO₂ shell while maintaining specific functional properties of their core material. A major challenge in the development of functional core–shell particles is the design of scalable high-yield processes that can meet large-scale industrial demand. Here, we present a safer formulation concept for flame-generated ENMs based on a one-step, in flight SiO₂ encapsulation process, which was recently introduced by the authors as a means for a scalable manufacturing of SiO₂-coated ENMs. First, the versatility of the SiO₂-coating process is demonstrated by applying it to four ENMs (CeO_2, ZnO, Fe₂O₃, Ag) marked by their prevalence in consumer products as well as their range in toxicity. The ENM-dependent coating fundamentals are assessed, and process parameters are optimized for each ENM investigated. The effects of the SiO₂-coating on core material structure, composition, and morphology, as well as the coating efficiency on each nanostructured material, are evaluated using state-of-the-art analytical methods (XRD, N₂ adsorption, TEM, XPS, isopropanol chemisorption). Finally, the biological interactions of SiO₂-coated vs uncoated ENMs are evaluated using cellular bioassays, providing valuable evidence for reduced toxicity for the SiO₂-coated ENMs. Results indicate that the proposed “safer by design” concept bears great promise for scaled-up application in industry in order to reduce the toxicological profile of ENMs for certain applications