Comparative assessment of total and inhalable dust sampler performance in hexavalent chromium measurement

Hexavalent chromium (Cr6+) is a known occupational carcinogen. Over the recent years, the increasing number of exposed workers and the emergence of serious health effects have led to considerable lowering of permissible exposure levels for Cr6+. Moreover, a number of methods have been developed for rapid and precise measurement of Cr6+concentrations. Given the importance of accurate measurements, this study was carried out to compare the performance of different samplers in relation to factors such as sampling height, sampling duration, and electroplating solution concentration. We used a hexavalent chromium generator fitted with a special sampling chamber and with proven ability to produce homogenous atmospheric concentrations. The performances of 4 samplers including IOM and CIS (as inhalable particle samplers) and Open and Closed-face cassettes (as total particle samplers) were examined through a simultaneous sampling technique. Sampling was done using the NIOSH 7600 method (samples were collected on PVC membrane filters with a pore size of 5.0 µm, at an air flow rate of 2.0 ± 0.1 l/min). Variables investigated with regard to their effects on sampler performance were sampling height (heights from bath solution: 35 and 50 cm), duration (30 and 180 min) and solution concentration (125 and 250 g/l). The measured concentrations ranged from 2 to 2725 µg.m-3. Analysis of the results in a completely randomized block design showed significant differences in performance between different samplers (P< 0.001). There were also differences between samplers at different heights and electroplating concentrations (P=0.0007). Multiple comparisons by Scheffe's method showed that the difference detected was due to the superior precision of the IOM (P<0.05). Overally, there were statistically significant differences between the performances of the studied samplers; Cr6+ concentrations at the studied heights (4.09, 8.68 µg.m-3), sampling duration (5.90, 6.88 µg.m-3), and bath concentration (2.73, 11.88 µg.m-3) had no significant effects on sampler performance. The CIS sampler underwent corrosion during acidic mist collection and thus can not be recommended for Cr6+ mist collection.