Metal workers' occupational exposure to particles and its effects on inflammation markers and pulmonary function

Tens of thousands of Finnish workers are exposed to metal particles. Respiratory exposure levels vary between the metal industries; in fact all the particulate emissions caused by industrial processes, especially if measured in particle number concentrations, have been poorly reported. Environmental exposure to outdoor particles and occupational exposure to welding fumes are known to cause harmful lung and cardiovascular effects as well as cancer, but the detailed mechanisms mediating these effects are not fully understood. Inflammation has been associated with the development of cancer and an inflammatory response has also been implicated in the development of atherosclerosis. The present study investigated occupational exposure to particles in welding workplaces and in a ferrochromium and stainless steel production line with particle exposures being measured in both mass and number concentrations. In addition, changes in welders’ blood inflammation markers and pulmonary function were studied in both workplace and the welding exposure tests, which were performed in workers with suspected occupational asthma. Ferrochromium and stainless steel workers' blood and lung inflammatory marker levels were compared to the levels observed in unexposed workers, and the associations between stainless steel workers particle exposure and levels of systemic and pulmonary inflammation markers were studied. In welding workplaces, the inhalable dust concentrations measured in the breathing zone were higher for welders than for sheet metal workers. Nevertheless, the exposure dose in sheet metal workers could be higher because most of the welders used effective respiratory protection while working, whereas sheet metal workers did not wear any respiratory protection. Employees using the MIG/MAG welding technique were exposed to higher concentrations of particulate matter than sheet metal workers. In the welding exposure tests, the average total particle number conentration varied between 1.7 × 106 and 3.2 × 106 particles/cm3. The particle size distribution was unimodal with most of the particles being about 430 nm in size. In the production of ferrochrome and stainless steel, exposure to particle mass and number concentrations were highest at the beginning of the production, during the sintering, ferrochromium smelting and steel melting phases. In contrast, exposure was the lowest at the end of the production chain at the cold rolling mill. Workers’ personal exposure was significantly reduced as compared to the process area particle concentration levels because workers spent about 85 % of their working time in control rooms where the particle concentrations were generally equivalent to the levels measured in office environments. Welding fume exposure caused a decrease in blood hemoglobin and erythrocytes as well as increasing the levels of leukocytes and neutrophils. Exposure also resulted in changes in blood interleukin-1β and E-selectin levels. No changes were found in the lung function tests in the workplaces during the working day, but after the welding exposure tests, a slight decrease in FEV1 and PEF values was observed. Among ferrochromium and stainless steel workers, no associations were found between the particle exposure and the inflammation markers. However, the baseline inflammation marker levels of the chromium-exposed groups differed slightly as compared to non-exposed controls. In conclusion, exposure to welding fume particles resulted in a mild acute systemic inflammation when measured as changes in blood inflammatory markers. Therefore, exposure to particles containing metals should be reduced by using control measures that improve occupational hygiene in all working environments where exposure to metal particles is likely. National Library of Medicine Classification: QV 290, QZ 150, WA 450, WB 284 Medical Subject Headings: Occupational Exposure; Air Pollutants, Occupational; Workplace; Particulate Matter; Dust; Metals; Stainless Steel; Chromium; Welding; Inflammation; Cytokines; Hemoglobins; Erythrocytes; Leukocytes; Neutrophils; Interleukin1beta; E-Selectin; Lung; Respiratory Function Tests; Asthma, Occupational Järvelä, Merja METALLITYÖNTEKIJÖIDEN TYÖPERÄINEN HIUKKASALTISTUMINEN JA VAIKUTUKSET TULEHDUSVÄLITTÄJÄAINEISIIN SEKÄ KEUHKOJEN TOIMINTAAN. Kuopio: Itä-Suomen yliopisto, 2018. Publications of the University of Eastern Finland Dissertation in Forestry and Natural Sciences ISBN: 978-952-61-2809-2 (nid.) ISSNL: 1798-5668 ISSN: 1798-5668 ISBN: 978-952-61-2810-8 (PDF) ISSN: 1798-5676 (PDF)