Quantitative monitoring and statistical modeling of dermal and inhalation exposure to monomeric and polymeric 1,6-hexamethylene diisocyanate during automotive spray-painting

Dermal and inhalation exposures to both the monomeric and polymeric forms of 1,6-hexamethylene diisocyanate (HDI) are associated with respiratory sensitization and occupational asthma. However, limited research has been performed on the evaluation of dermal and inhalation exposure to individual monomeric and polymeric HDI in the automotive refinishing industry due to the lack of specific and sensitive analytical methods and measurement techniques. The objective of this research was to develop methodology to quantify dermal and inhalation exposure to HDI and its oligomers (uretidone, biuret, and isocyanurate), to use this methodology to obtain detailed exposure profiles for 47 automotive painters in North Carolina and Washington State, and to use linear mixed modeling to identify the primary determinants of analyte-specific breathing-zone concentrations (BZCs) and dermal concentrations. A highly sensitive and specific liquid chromatography/mass spectrometry method capable of quantifying monomeric and polymeric HDI in air, tape-stripped skin, and paint samples was developed and validated in the occupational setting. Isocyanurate represented the predominant species (i.e., > 90%) of the HDI-based polyisocyanates in sampled paint, air, and skin. The tape-strip sampling methodology that we used had superior collection efficiency and specificity compared to other methods in the literature, while our air measurements of HDI and isocyanurate depended on the type of sampler (i.e., one- or two-stage) used to monitor the breathing-zone. The primary determinants of BZC and dermal concentration were unique to each analyte. As expected, for each of the measured polyisocyanate species, paint concentration was a significant predictor of BZC, and the product of BZC and paint time was a significant predictor of dermal concentration. The models developed in this study provided us with a better understanding of the processes leading to dermal and inhalation exposure to monomeric and polymeric HDI. This understanding was used to identify and quantitatively characterize control interventions for reducing polyisocyanate exposures for the ultimate goal of protecting automotive spray-painters from potential adverse health effects, such as occupational asthma

Flame retardants, dioxins, and furans in air and on firefighters’ protective ensembles during controlled residential firefighting

Structure fires that involve modern furnishings may emit brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs), as well as brominated and chlorinated dioxins and furans, into the environment. The goal of this study was to quantify the airborne and personal protective equipment (PPE) contamination levels of these compounds during controlled residential fires in the U.S., and to evaluate gross-decontamination measures

Factors affecting variability in the urinary biomarker 1,6-hexamethylene diamine in workers exposed to 1,6-hexamethylene diisocyanate

Although urinary 1,6-hexamethylene diamine (HDA) is a useful biomarker of exposure to 1,6-hexamethylene diisocyanate (HDI), a large degree of unexplained intra- and inter-individual variability exists between estimated HDI exposure and urine HDA levels. We investigated the effect of individual and workplace factors on urine HDA levels using quantitative dermal and inhalation exposure data derived from a survey of automotive spray painters exposed to HDI. Painters' dermal and breathing-zone HDI-exposures were monitored over an entire workday for up to three separate workdays, spaced approximately one month apart. One urine sample was collected before the start of work with HDI-containing paints, and multiple samples were collected throughout the workday. Using mixed effects multiple linear regression modeling, coverall use resulted in significantly lower HDA levels (p = 0.12), and weekday contributed to significant variability in HDA levels (p = 0.056). We also investigated differences in urine HDA levels stratified by dichotomous and classification covariates using analysis of variance. Use of coveralls (p = 0.05), respirator type worn (p = 0.06), smoker status (p = 0.12), paint-booth type (p = 0.02), and more than one painter at the shop (p = 0.10) were all found to significantly affect urine HDA levels adjusted for creatinine concentration. Coverall use remained significant (p = 0.10), even after adjusting for respirator type. These results indicate that the variation in urine HDA level is mainly due to workplace factors and that appropriate dermal and inhalation protection is required to prevent HDI exposure

Hemoglobin adducts in workers exposed to 1,6-hexamethylene diisocyanate

We investigated the utility of 1,6-hexamethylene diamine (HDA) hemoglobin adducts as biomarkers of exposure to 1,6-hexamethylene diisocyanate (HDI) monomer. Blood samples from 15 spray painters applying HDI-containing paint were analyzed for hemoglobin HDA (HDA-Hb) and N-acetyl-1,6-hexamethylene diamine (monoacetyl-HDA-Hb) by GC-MS. HDA-Hb was detected in the majority of workers (≤1.2–37 ng/g Hb), whereas monoacetyl-HDA-Hb was detected in one worker (0.06 ng/g Hb). The stronger, positive association between HDA-Hb and cumulative HDI exposure (r2 = 0.3, p < 0.06) than same day exposure (p ≥ 0.13) indicates long-term elimination kinetics for HDA-Hb adducts. This association demonstrates the suitability of HDA-Hb adducts for further validation as a biomarker of HDI exposure

Systemic Exposure to PAHs and Benzene in Firefighters Suppressing Controlled Structure Fires

Turnout gear provides protection against dermal exposure to contaminants during firefighting; however, the level of protection is unknown. We explored the dermal contribution to the systemic dose of polycyclic aromatic hydrocarbons (PAHs) and other aromatic hydrocarbons in firefighters during suppression and overhaul of controlled structure burns. The study was organized into two rounds, three controlled burns per round, and five firefighters per burn. The firefighters wore new or laundered turnout gear tested before each burn to ensure lack of PAH contamination. To ensure that any increase in systemic PAH levels after the burn was the result of dermal rather than inhalation exposure, the firefighters did not remove their self-contained breathing apparatus until overhaul was completed and they were >30 m upwind from the burn structure. Specimens were collected before and at intervals after the burn for biomarker analysis. Urine was analyzed for phenanthrene equivalents using enzyme-linked immunosorbent assay and a benzene metabolite (s-phenylmercapturic acid) using liquid chromatography/tandem mass spectrometry; both were adjusted by creatinine. Exhaled breath collected on thermal desorption tubes was analyzed for PAHs and other aromatic hydrocarbons using gas chromatography/mass spectrometry. We collected personal air samples during the burn and skin wipe samples (corn oil medium) on several body sites before and after the burn. The air and wipe samples were analyzed for PAHs using a liquid chromatography with photodiode array detection. We explored possible changes in external exposures or biomarkers over time and the relationships between these variables using non-parametric sign tests and Spearman tests, respectively. We found significantly elevated (P < 0.05) post-exposure breath concentrations of benzene compared with pre-exposure concentrations for both rounds. We also found significantly elevated post-exposure levels of PAHs on the neck compared with pre-exposure levels for round 1. We found statistically significant positive correlations between external exposures (i.e. personal air concentrations of PAHs) and biomarkers (i.e. change in urinary PAH metabolite levels in round 1 and change in breath concentrations of benzene in round 2). The results suggest that firefighters wearing full protective ensembles absorbed combustion products into their bodies. The PAHs most likely entered firefighters’ bodies through their skin, with the neck being the primary site of exposure and absorption due to the lower level of dermal protection afforded by hoods. Aromatic hydrocarbons could have been absorbed dermally during firefighting or inhaled during the doffing of gear that was off-gassing contaminants.National Institute for Occupational Safety and Health (NIOSH) by intramural award under the National Occupational Research AgendaOpe

Contamination of firefighter personal protective equipment and skin and the effectiveness of decontamination procedures

Firefighters’ skin may be exposed to chemicals via permeation/penetration of combustion byproducts through or around personal protective equipment (PPE) or from the cross-transfer of contaminants on PPE to the skin. Additionally, volatile contaminants can evaporate from PPE following a response and be inhaled by firefighters. Using polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) as respective markers for non-volatile and volatile substances, we investigated the contamination of firefighters’ turnout gear and skin following controlled residential fire responses. Participants were grouped into three crews of twelve firefighters. Each crew was deployed to a fire scenario (one per day, four total) and then paired up to complete six fireground job assignments.Wipe sampling of the exterior of the turnout gear was conducted pre- and post-fire.Wipe samples were also collected from a subset of the gear after field decontamination. VOCs off-gassing from gear were also measured pre-fire, post-fire, and post-decon. Wipe sampling of the firefighters’ hands and neck was conducted pre- and post-fire. Additional wipes were collected after cleaning neck skin. PAH levels on turnout gear increased after each response and were greatest for gear worn by firefighters assigned to fire attack and to search and rescue activities. Field decontamination using dish soap, water, and scrubbing was able to reduce PAH contamination on turnout jackets by a median of 85%. Off-gassing VOC levels increased post-fire and then decreased 17–36 min later regardless of whether field decontamination was performed. Median post-fire PAH levels on the neck were near or below the limit of detection (<24 micrograms per square meter [μg/m2]) for all positions. For firefighters assigned to attack, search, and outside ventilation, the 75th percentile values on the neck were 152, 71.7, and 39.3 μg/m2, respectively. Firefighters assigned to attack and search had higher post-fire median hand contamination (135 and 226 μg/m2, respectively) than other positions (<10.5 μg/m2). Cleansing wipes were able to reduce PAH contamination on neck skin by a median of 54%.This study was funded through a U.S. Department of Homeland Security, Assistance to Firefighters Grant (EMW-2013- FP-00766). This project was also made possible through a partnership with the CDC Foundation.Ope

Thermal response to firefighting activities in residential structure fires: impact of job assignment and suppression tactic

Firefighters’ thermal burden is generally attributed to high heat loads from the fire and metabolic heat generation, which may vary between job assignments and suppression tactic employed. Utilising a full-sized residential structure, firefighters were deployed in six job assignments utilising two attack tactics (1. Water applied from the interior, or 2. Exterior water application before transitioning to the interior). Environmental temperatures decreased after water application, but more rapidly with transitional attack. Local ambient temperatures for inside operation firefighters were higher than other positions (average ~10–30 °C). Rapid elevations in skin temperature were found for all job assignments other than outside command. Neck skin temperatures for inside attack firefighters were ~0.5 °C lower when the transitional tactic was employed. Significantly higher core temperatures were measured for the outside ventilation and overhaul positions than the inside positions (~0.6–0.9 °C). Firefighters working at all fireground positions must be monitored and relieved based on intensity and duration. Practitioner Summary: Testing was done to characterise the thermal burden experienced by firefighters in different job assignments who responded to controlled residential fires (with typical furnishings) using two tactics. Ambient, skin and core temperatures varied based on job assignment and tactic employed, with rapid elevations in core temperature in many roles.This work was supported by the Department of Homeland Security Fire Prevention and Safety Grant [#EMW-2013-FP-00766].Ope

Exposure to a firefighting overhaul environment without respiratory protection increases immune dysregulation and lung disease risk

Firefighting activities appear to increase the risk of acute and chronic lung disease, including malignancy. While self-contained breathing apparatuses (SCBA) mitigate exposures to inhalable asphyxiates and carcinogens, firefighters frequently remove SCBA during overhaul when the firegrounds appear clear of visible smoke. Using a mouse model of overhaul without airway protection, the impact of fireground environment exposure on lung gene expression was assessed to identify transcripts potentially critical to firefighter-related chronic pulmonary illnesses. Lung tissue was collected 2 hrs post-overhaul and evaluated via whole genome transcriptomics by RNA-seq. Although gas metering showed that the fireground overhaul levels of carbon monoxide (CO), carbon dioxide (CO2), hydrogen cyanine (HCN), hydrogen sulfide (H2S) and oxygen (O2) were within NIOSH ceiling recommendations, 3852 lung genes were differentially expressed when mice exposed to overhaul were compared to mice on the fireground but outside the overhaul environment. Importantly, overhaul exposure was associated with an up/down-regulation of 86 genes with a fold change of 1.5 or greater (p<0.5) including the immunomodulatory-linked genes S100a8 and Tnfsf9 (downregulation) and the cancer-linked genes, Capn11 and Rorc (upregulation). Taken together these findings indicate that, without respiratory protection, exposure to the fireground overhaul environment is associated with transcriptional changes impacting proteins potentially related to inflammation-associated lung disease and cancer.This work was supported by the Department of Homeland Security Fire Prevention and Safety Grant #EMW-2013-FP-00766 to G.H. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ope

Airborne Isocyanate Exposures in the Collision Repair Industry and a Comparison to Occupational Exposure Limits

Isocyanate exposure was evaluated in 33 spray painters from 25 Washington State autobody shops. Personal breathing zone samples (n = 228) were analyzed for isophorone diisocyanate (IPDI) monomer, 1,6-hexamethylene diisocyanate (HDI) monomer, IPDI polyisocyanate, and three polyisocyanate forms of HDI. The objective was to describe exposures to isocyanates while spray painting, compare them with short-term exposure limits (STELs), and describe the isocyanate composition in the samples. The composition of polyisocyanates (IPDI and HDI) in the samples varied greatly, with maximum amounts ranging from up to 58% for HDI biuret to 96% for HDI isocyanurate. There was a significant inverse relationship between the percentage composition of HDI isocyanurate to IPDI and to HDI uretdione. Two 15-min STELs were compared: (1) Oregon's Occupational Safety and Health Administration (OR-OSHA) STEL of 1000 μg/m3 for HDI polyisocyanate, and (2) the United Kingdom's Health and Safety Executive (UK-HSE) STEL of 70 μg NCO/m3 for all isocyanates. Eighty percent of samples containing HDI polyisocyanate exceeded the OR-OSHA STEL while 98% of samples exceeded the UKHSE STEL. The majority of painters (67%) wore half-face air-purifying respirators while spray painting. Using the OROSHA and the UK-HSE STELs as benchmarks, 21% and 67% of painters, respectively, had at least one exposure that exceeded the respirator's OSHA-assigned protection factor. A critical review of the STELs revealed the following limitations: (1) the OR-OSHA STEL does not include all polyisocyanates, and (2) the UK-HSE STEL is derived from monomeric isocyanates, whereas the species present in typical spray coatings are polyisocyanates. In conclusion, the variable mixtures of isocyanates used by autobody painters suggest that an occupational exposure limit is required that includes all polyisocyanates. Despite the limitations of the STELs, we determined that a respirator with an assigned protection factor of 25 or greater is required to protect against isocyanate exposures during spray painting. Consequently, half-face air-purifying respirators, which are most commonly used and have an assigned protection factor of 10, do not afford adequate respiratory protection