Reduction of hexavalent chromium collected on PVC filters

Chromium exists at various valences, including elemental, trivalent, and he xavalent chromium, and undergoes reduction-oxidation reactions in the envir onment. Since hexavalent chromium is known as a human carcinogen, it is mos t important to evaluate the oxidation-reduction characteristics of the hexa valent chromium species. Although hexavalent chromium can be reduced to tri valent state, the detailed information on this in workplace environments is limited. The purpose of this study was to investigate hexavalent chromium reduction in time in various conditions. A pilot chrome plating operation w as prepared and operated in a laboratory for this study. There was evidence that the hexavalent chromium was reduced by time after mist generation. Th e percentage ratio (with 95% confidence intervals in parentheses) of hexava lent chromium to total chromium was almost 100% (99.1 similar to 102.3) imm ediately after mist generation, and was reduced to 87.4% (84.8 similar to 8 9.9) at 1 hour and 81.0% (78.3 similar to 83.5) at 2 hours, respectively. A nother test indicated that hexavalent chromium collected on PVC filters was also reduced by time after sampling. Hexavalent chromium was reduced to 90 .8% (88.2 similar to 93.3) at 2 hours after sampling. It also was found tha t hexavalent chromium was reduced during storage in air. It is recommended that air samples of hexavalent chromium be protected against reduction duri ng storage.