Relationships between inhalable and total hexavalent chromium exposures in steel passivation, welding and electroplating operations of Ontario

The main aim of the study was to assess the relationship between inhalable hexavalent chromium and "total" hexavalent chromium. Air sampling was conducted at steel passivation operation of a steel manufacturer at a stainless steel welding operation and at two hard chrome electroplaters. Air samples were taken side-by-side for "total" dust using closed-face 37-mm diameter cassette samplers and for inhalable dust using Institute of Occupational Medicine inhalable samplers. A total of 40 pairs of total and inhalable dust samples were collected and later analyzed. The range of "total" dust and inhalable dust concentrations in μg/m³ measured were 30-410 and 0.02 to 740 respectively for steel passivation; 260 to 1520 and 477 to 6970 for welding; and 0.01 to 1500 and 204 to 2130 for electroplaters. The range of "total" dust hexavalent chromium and inhalable dust hexavalent chromium concentrations in μg/m³ were 0.02-89 and 0.02 to 150 respectively for steel making; 4.1 to 4.9 and 2.2 to 6.9 for welding and 0.01 to 9.3 and 0.01 to 21 for electroplaters. A linear relationship between inhalable hexavalent chromium and "total" hexavalent chromium was found with a slope of 1.4 (CI:1.3, 1.5) and 0 offset. A ratio of 1.4 can thus be used as a conversion factor to convert previous data of hexavalent chromium taken on "total" dust basis to inhalable hexavalent chromium concentrations.