Metal occupational exposure limits mainly focus on total content of the respective metals of interest. The methods applied for trace metal analysis in occupational health and safety laboratories are usually standardized to pragmatic consensus digestion schemes, ensuring comparability of results. The objective of the present study entailed the evaluation of a recently developed HNO3-only microwave-assisted digestion procedure by comparison with the German consensus hot-block digestion and other national digestion schemes. An inter-laboratory comparison test with participation of nine national occupational health and safety laboratories from Europe and North America was organized. For adequate emulation of what workers are at risk of inhaling four different industrial metal processing workplace dusts (electronic recycling, high-speed steel grinding, cylinder head cleaning, and battery combustion ash) were homogenized and sieved to the particle size < 100 µm diameter at IFA. The participants were asked to process air sample-typical amounts according to the German hot-plate technique, the IFA microwave-assisted digestion scheme as well as their national or in-house conventional digestion method for airborne dust and analyze for Cd, Co, Cr, Co, Fe, Mg, Ni, Pb, and Zn. Recoveries (relative to consensus open-vessel digestion) obtained for the new IFA microwave-assisted digestion were between 88 and 114% and relative reproducibility standard deviations were <10% for most metals of interest. The in-house digestion procedures applied varied widely but (whether microwave, hot block, or open vessel) yielded comparable results for the predominantly elemental alloy type dusts supplied. Results become more diverse for the combustion dust, especially if a combination of microwave-assisted digestion procedures with high temperatures and hydrofluoric acid is applied. ISO 15202-2 is currently being revised; this digestion procedure will be included as a possible variant in annex 2.

Metallic dust is a heterogeneous substance with respiratory sensitizing properties. Its long term exposure adversely affected lung function, thus may cause acute or chronic respiratory diseases.
A cross-sectional study was conducted in a steel factory in Terengganu, Malaysia to assess the metal dust exposure and its relationship to lung function values among 184 workers. Metal dust concentrations values (Co, Cr, and Ni) for each worker were collected using air personal sampling. Lung function values (FEV1, FVC, and %FEV1/FVC) were determined using spirometer.
Exposure to cobalt and chromium were 1-3 times higher than permissible exposure limit (PEL) while nickel was not exceeding the PEL. Cumulative of chromium was the predictor to all lung function values (FEV1, FVC, and %FEV1/FVC). Frequency of using mask was positively associated with FVC (Adj b = 0.263, P = 0.011) while past respiratory illnesses were negatively associated with %FEV1/FVC (Adj b = -1.452, P = 0.026). Only few workers (36.4%) were found to wear their masks all times during the working hours.
There was an exposure-response relationship of cumulative metal dust exposure with the deterioration of lung function values. Improvement of control measures as well as proper and efficient use or personal protection equipment while at work could help to protect the respiratory health of workers.

Head and neck cancers account for an estimated 549,000 global cancer diagnoses each year. While tobacco use, alcohol consumption, and HPV16 infection are considered to be the major risk factors for this disease, occupational risk factors, including exposure to asbestos, have also been described, although dust exposures other than asbestos have been historically understudied. We have investigated the relationship between occupational exposures to five types of dusts, including sawdust, concrete dust, leather dust, metal dust, and chimney soot, and head and neck squamous cell carcinomas (HNSCC) in the greater Boston area. We report findings from a population-based case-control study involving 951 incident HNSCC cases and 1193 controls, frequency matched on age (±3 years), sex, and town/neighborhood of residence. Multivariable logistic regression was used to assess the association between occupational exposure to each type of dust and HNSCC, overall and by primary tumor site. After adjusting for age, sex, race, smoking, alcohol consumption, education, and HPV16 serology, laryngeal carcinoma risk increased for each decade of occupational exposure to sawdust (OR = 1.2, 95% CI: 1.0, 1.3) and metal dust (OR = 1.2, 95% CI: 1.0, 1.4); and HNSCC risk increased for each decade of occupational leather dust exposure (OR = 1.5, 95% CI: 1.2, 1.9). We have provided evidence for an association between occupational sawdust and metal dust and laryngeal squamous cell carcinoma, and leather dust and HNSCC, with increasing risk with longer duration at the exposed occupation.