Impact Of Environmental Exposure To Hexavalent Chromium On Residents’ Health: Association Of Urinary Chromium And Hematological And Biochemical Indicators

BackgroundHexavalent chromium is recognized as a definitely carcinogenic to humans by_the International Agency for Research on Cancer (IARC). Effects of low-level exposure to hexavalent chromium on early hazard to humans are increasingly concerned about. Studies on occupational groups showed that exposure to hexavalent chromium could cause certain alterations in hematological and biochemical parameters. But there are differences between chromates exposed workers and general population in the mode of exposure. The patterns, duration and doses of exposure to hexavalent chromium in the residents living at chromium-polluted areas are so different from those in occupationally-exposed groups. It is essential to recognize potential health effects of chromium, especially its early clinical indicators, on the residents exposed to it. There seldom is a typical study site for epidemiological evaluation of the effects of exposure to environmental chromium pollution on general population, and association between exposure to hexavalent chromium and adverse health effects is relatively less studied, particularly in a site with relatively longer exposure.ObjectiveThis study was designed to quantify individual level of exposure to hexavalent chromium in people living at an environmental chromium-polluted area and explore its effects on their health outcomes in local residents, with correlation analysis for their urinary level of hexavalent chromium and clinical symptoms and signs, and routine blood examination indices.MethodsA cross-sectional study was conducted in the residents living in an area where there is an alloy plant discharging waste water containing hexavalent chromium for more than 50 years, affecting six kilometers all around in Jinzhou, Liaoning province, northeast China.135 residents aged 18 years or above living there for a long time without occupational chromium exposure were selected by cluster sampling. A questionnaire-based survey was applied to investigate their major health outcomes related to chromium exposure for the interviewees, including clinical symptoms and signs. Their blood and urine specimens were collected to test hexavalent chromium-related biomarkers. Association between urinary level of hexavalent chromium and clinical symptoms and signs was studied to explore health effects in local residents by environmental chromium pollution.Results1. Among the residents studied, geometric mean of urinary concentration of hexavalent chromium was 23.91 μg/L, significantly higher than that of the national average (0.53 μg/L). Prevalence of related symptoms of digestive and respiratory systems were the highest in those with moderate and high urinary level of hexavalent chromium, respectively.2. A significant dose-response relationship between urinary hexavalent chromium level and red blood cell count (RBC), mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV), respectively was observed. Abnormal percentage of MCV and mean corpuscular hemoglobin concentration (MCHC) increased with urinary level of hexavalent chromium, which correlated with MCH and lymphocyte (LYMP) count, respectively, in women and in those aged 60 years or less, correlated negatively with RBC count only in women, and correlated negatively with MCHC only in men.3. A significant dose-response relationship between urinary level of hexavalent chromium and some parameters of liver function tests, such as serum levels of total protein, globulin and direct bilirubin, was observed, and a reverse dose-response relationship between urinary level of hexavalent chromium and ratio of serum albumin to globulin levels was observed. Further stratified analysis showed an association between serum total protein, globulin and low-density lipoprotein-cholesterol, respectively, in those aged 60 years and over. Association between urinary level of hexavalent chromium and serum level of globulin was observed only in women, and reverse association between urinary level of hexavalent chromium and serum glucose level was observed only in women. An association between urinary level of hexavalent chromium and serum direct bilirubin was observed in men. Ratio of serum levels of albumin to globulin associated significantly with urinary level of hexavalent chromium in different groups (P<0.05).ConclusionsCertain adverse health effects have been occurred in the residents living in the chromium-polluted area for a long time, and their urinary level of hexavalent chromium is higher than that of the national average. Long-term exposure to hexavalent chromium could damage to their blood indices, and cause some digestive and respiratory symptoms.