Chromium urine concentration and effects on lymphocyte subpopulations in children

We conducted an epidemiological study on exposure to a toxic waste incineration plant that focused on heavy metals and organochlorines and their potential health effect. In this paper we concentrate on whether chromium urine concentration (CrU) in 24 h urine samples was associated with changes in the number of lymphocytes in blood samples. The potential confounding effects of age, gender, environmental tobacco smoke (ETS), blood lead, blood mercury and polychlorinated biphenyls (PCBs) in blood, as well as the concentration of mercury, cadmium and arsenic in 24 h urine samples were controlled for. The numbers of total lymphocytes, T lymphocytes, B lymphocytes, natural killer cells, CD4 helper and CD8 cytotoxic T cells were determined with fluorescence-activated cell sorter (FACS). CrU was categorized into four groups: below detection limit (0.08 μg l⁻¹); detection limit to 0.13 μg l⁻¹; 0.14–0.22 μg l⁻¹; 0.24 μg l⁻¹ and above. The groups were analysed as predictors of different lymphocyte subpopulations in separate multiple linear regression models adjusted for potential confounders (age, gender, passive smoking, PCB, lead and mercury in whole blood, arsenic, cadmium, mercury in 24 h urine).

CrU, lymphocyte counts and information on questionnaire data were available for 315 children, aged 7–10 years. We found a statistically significant negative association between the CrU groups and the total T cell count, T-helper (CD4) cell count, absolute number of CD4+CD25+ helper T cells, and CD4+CD45RO+ memory T helper cells. No association was found for CrU groups and white blood cell, total lymphocyte, natural killer cell and B cell counts. With the exception of ETS and blood lead level, no other predictor was of importance for the lymphocytes. The rank correlation suggested a reduction in the number of infections when chromium was increased, even though the cause and effect relationship was not clear. The results illustrated a possible effect of chromium on T-lymphocytes. Copyright © 1999 John Wiley & Sons, Ltd.