Occupational exposure to formaldehyde and alterations in lymphocyte subsets

Background: Formaldehyde is used in many occupational settings, most notably in manufacturing, health care, and embalming. Formaldehyde has been classified as a human carcinogen, but its mechanism of action remains uncertain. Methods: We carried out a cross-sectional study of 43 formaldehyde-exposed workers and 51 unexposed age and sex-matched controls in Guangdong, China to study formaldehyde's early biologic effects. To follow up our previous report that the total lymphocyte count was decreased in formaldehyde-exposed workers compared with controls, we evaluated each major lymphocyte subset (i.e., CD4⁺ T cells, CD8⁺ T cells, natural killer [NK] cells, and B cells) and T cell lymphocyte subset (CD4⁺ naïve and memory T cells, CD8⁺ naïve and memory T cells, and regulatory T cells). Linear regression of each subset was used to test for differences between exposed workers and controls, adjusting for potential confounders. Results: Total NK cell and T cell counts were about 24% (P=0.037) and 16% (P=0.0042) lower, respectively, among exposed workers. Among certain T cell subsets, decreased counts among exposed workers were observed for CD8⁺ T cells (P=0.026), CD8⁺ effector memory T cells (P=0.018), and regulatory T cells (CD4⁺FoxP3⁺: P=0.04; CD25⁺FoxP3⁺: P=0.008). Conclusions: Formaldehyde-exposed workers experienced decreased counts of NK cells, regulatory T cells, and CD8⁺ effector memory T cells; however, due to the small sample size; these findings need to be confirmed in larger studies.