"In Litero" Screening: Retrospective Evaluation of Clinical Evidence to Establish a Reference List of Human Chemical Respiratory Sensitizers.

Despite decades of investigation, test methods to identify respiratory sensitizers remain an unmet regulatory need. In order to support the evaluation of New Approach Methodologies in development, we sought to establish a reference set of low molecular weight respiratory sensitizers based on case reports of occupational asthma. In this context, we have developed an "in litero" approach to identify cases of low molecular weight chemical exposures leading to respiratory sensitization in clinical literature. We utilized the EPA-developed Abstract Sifter literature review tool to maximize the retrieval of publications relevant to respiratory effects in humans for each chemical in a list of chemicals suspected of inducing respiratory sensitization. The literature retrieved for each of these candidate chemicals was sifted to identify relevant case reports and studies, and then evaluated by applying defined selection criteria. Clinical diagnostic criteria were defined around exposure history, respiratory effects, and specific immune response to conclusively demonstrate occupational asthma as a result of sensitization, rather than irritation. This approach successfully identified 28 chemicals that can be considered as human respiratory sensitizers and used to evaluate the performance of NAMs as part of a weight of evidence approach to identify novel respiratory sensitizers. Further, these results have immediate implications for the development and refinement of predictive tools to distinguish between skin and respiratory sensitizers. A comparison of the protein binding mechanisms of our identified "in litero" clinical respiratory sensitizers shows that acylation is a prevalent protein binding mechanism, in contrast to Michael addition and Schiff base formation common to skin sensitizers. Overall, this approach provides an exemplary method to evaluate and apply human data as part of the weight of evidence when establishing reference chemical lists.

Hazard identification and consumer safety characterization for trans-1-chloro-3,3,3-trifluoropropene (trans-1233zd).

Trans-1233zd was developed as a refrigerant and propellant in consumer products; its toxicity has been studied extensively. The scope of this assessment is to apply the confirmed NOAEC to conduct Benchmark Dose Modeling (BMD) and determine the Point of Departure (POD). In a previously published 13-week inhalation study, a NOAEC was identified at 4000 ppm. Due to uncertainty concerning the cardiac lesion, an external pathology peer review of heart tissues was undertaken using published best practices and consistent nomenclature and diagnostic criteria. The cardiac lesion observed at 4000 ppm was considered to be spontaneous based on lesion location and microscopic features. BMD was applied to derive the BMDL05 and BMDL10; the more conservative BMDL05 was used as the POD for risk assessment to calculate the Reference Exposure Levels (RELs). The 2-Box Air Dispersion Model was used to calculate the exposure to consumer products. Both the acute and chronic exposure concentrations calculated were compared to the acute and chronic RELs. The acute and chronic exposure to trans-1233zd in the assessed consumer products are below the RELs and deemed safe for their intended uses.

Exploring the science, safety, and benefits of air care products: perspectives from the inaugural air care summit.

Seventy-one percent of US households purchase air care products. Air care products span a diverse range of forms, including scented aerosol sprays, pump sprays, diffusers, gels, candles, and plug-ins. These products are used to eliminate indoor malodors and to provide pleasant scent experiences. The use of air care products can lead to significant benefits as studies have shown that indoor malodor can cause adverse effects, negatively impacting quality of life, hygiene, and the monetary value of homes and cars, while disproportionately affecting lower income populations. Additionally, studies have also shown that scent can have positive benefits related to mood, stress reduction, and memory enhancement among others. Despite the positive benefits associated with air care products, negative consumer perceptions regarding the safety of air care products can be a barrier to their use. During the inaugural Air Care Summit, held on 18 May 2018 in the Washington, DC, metropolitan area, multidisciplinary experts including industry stakeholders, academics, and scientific and medical experts were invited to share and assess the existing data related to air care products, focusing on ingredient and product safety and the benefits of malodor removal and scent. At the Summit's completion, a panel of independent experts representing the fields of pulmonary medicine, medical and clinical toxicology, pediatric toxicology, basic science toxicology, occupational dermatology and experimental psychology convened to review the data presented, identify potential knowledge gaps, and suggest future research directions to further assess the safety and benefits of air care products.

Human health risk evaluation of selected VOC, SVOC and particulate emissions from scented candles.

Airborne compounds in the indoor environment arise from a wide variety of sources such as environmental tobacco smoke, heating and cooking, construction materials as well as outdoor sources. To understand the contribution of scented candles to the indoor load of airborne substances and particulate matter, candle emission testing was undertaken in environmentally controlled small and large emission chambers. Candle emission rates, calculated on the basis of measured chamber concentrations of volatile and semi-volatile organic compounds (VOC, SVOC) and particulate matter (PM), were used to predict their respective indoor air concentrations in a standard EU-based dwelling using 2 models: the widely accepted ConsExpo 1-box inhalation model and the recently developed RIFM 2-box indoor air dispersion model. The output from both models has been used to estimate more realistic consumer exposure concentrations of specific chemicals and PM in candle emissions. Potential consumer health risks associated with the candle emissions were characterized by comparing the exposure concentrations with existing indoor or ambient air quality guidelines or, where not existent, to established toxicity thresholds. On the basis of this investigation it was concluded that under normal conditions of use scented candles do not pose known health risks to the consumer.

Amorphous silica particles promote inflammatory gene expression through the redox sensitive transcription factor, AP-1, in alveolar epithelial cells.

Ultrafine particulate (UFP) matter, from environmental or industrial exposure, can induce expression of inflammatory mediators and promote production of reactive oxygen species. Previous studies showed various cellular stresses activate signaling pathways operating through specific transcription factors (TFs), activator protein (AP)-1 and nuclear factor (NF)-kappaB, known to regulate inflammatory gene expression. Exposing MLE15 cells to inflammatory, or UFP, stimuli increased macrophage inflammatory protein (MIP)-2 protein, in the absence of the NF = kappaB inhibitor IkappaBc degradation, synergistically increasing in the presence of proteosomal inhibition. Although thiol antioxidants attenuate MIP-2 induction, mitogen-activated protein kinase (MAPK) inhibitors significantly inhibit MIP-2 protein production. This suggests UFP promote inflammatory gene expression through the redox responsive TF AP-1.

Use of indicator cell lines for determining inflammatory gene changes and screening the inflammatory potential of particulate and non-particulate stimuli.

Ultrafine particulate matter, from environmental or industrial exposure, can induce the expression of inflammatory mediators and promote the production of reactive oxygen species (ROS), which can damage the alveolar epithelium of the lung. Previous studies have shown that various cellular stresses can activate signaling pathways that operate through the specific transcription factors (TF), AP-1, and nuclear factor (NF)-kappaB that are known to regulate inflammatory gene expression. Persistent inflammation can induce a cascade of events that precedes the development of both acute and chronic fibrosis. From a murine Type II epithelial cell line, MLE15, a stable luciferase-transfected line, MLE15Luc2, was created. The luciferase reporter, operating under the guidance of a truncated human interleukin (IL)-8 promoter, contains NF-kappaB and AP-1 DNA binding sites. MLE15Luc2 cells were exposed to inflammatory or particulate stimuli, of varying size fractions and composition, under standard culture conditions, and inflammatory gene transcription, represented by luciferase enzyme activity, was determined. IkappaBalpha degradation appeared to be incongruent to changes in luciferase activity. The results were compared to those obtained using a stable luciferase-transfected human cell line, A549Luc1. Time-course data demonstrated increased luciferase enzyme activity, peaking by 6 h postexposure, and returning to baseline by 24 h, regardless of stimulus, in the absence of enhanced cytotoxicity. This suggests that key regulatory functions in these transfected cell lines are not clearly understood. These transfected cell lines may be useful for determining the inflammatory potential of various types of particulate and/or non-particulate stimuli; however, conclusive signaling information cannot be gained from their use alone.