Hanlin Huang

Occupational exposure to formaldehyde, hematotoxicity, and leukemia-specific chromosome changes in cultured myeloid progenitor cells.

There are concerns about the health effects of formaldehyde exposure, including carcinogenicity, in light of elevated indoor air levels in new homes and occupational exposures experienced by workers in health care, embalming, manufacturing, and other industries. Epidemiologic studies suggest that formaldehyde exposure is associated with an increased risk of leukemia. However, the biological plausibility of these findings has been questioned because limited information is available on the ability of formaldehyde to disrupt hematopoietic function. Our objective was to determine if formaldehyde exposure disrupts hematopoietic function and produces leukemia-related chromosome changes in exposed humans. We examined the ability of formaldehyde to disrupt hematopoiesis in a study of 94 workers in China (43 exposed to formaldehyde and 51 frequency-matched controls) by measuring complete blood counts and peripheral stem/progenitor cell colony formation. Further, myeloid progenitor cells, the target for leukemogenesis, were cultured from the workers to quantify the level of leukemia-specific chromosome changes, including monosomy 7 and trisomy 8, in metaphase spreads of these cells. Among exposed workers, peripheral blood cell counts were significantly lowered in a manner consistent with toxic effects on the bone marrow and leukemia-specific chromosome changes were significantly elevated in myeloid blood progenitor cells. These findings suggest that formaldehyde exposure can have an adverse effect on the hematopoietic system and that leukemia induction by formaldehyde is biologically plausible, which heightens concerns about its leukemogenic potential from occupational and environmental exposures. Cancer Epidemiol Biomarkers Prev; 19(1); 80–8.

Occupational exposure to trichloroethylene is associated with a decline in lymphocyte subsets and soluble CD27 and CD30 markers

Occupational cohort and case-control studies suggest that trichloroethylene (TCE) exposure may be associated with non-Hodgkin lymphoma (NHL) but findings are not consistent. There is a need for mechanistic studies to evaluate the biologic plausibility of this association. We carried out a cross-sectional molecular epidemiology study of 80 healthy workers that used TCE and 96 comparable unexposed controls in Guangdong, China. Personal exposure measurements were taken over a three-week period before blood collection. Ninety-six percent of workers were exposed to TCE below the current US Occupational Safety and Health Administration Permissible Exposure Limit (100 p.p.m. 8 h time-weighted average), with a mean (SD) of 22.2 (36.0) p.p.m. The total lymphocyte count and each of the major lymphocyte subsets including CD4+ T cells, CD8+ T cells, natural killer (NK) cells and B cells were significantly decreased among the TCE-exposed workers compared with controls (P < 0.05), with evidence of a dose-dependent decline. Further, there was a striking 61% decline in sCD27 plasma level and a 34% decline in sCD30 plasma level among TCE-exposed workers compared with controls. This is the first report that TCE exposure under the current Occupational Safety and Health Administration workplace standard is associated with a decline in all major lymphocyte subsets and sCD27 and sCD30, which play an important role in regulating cellular activity in subsets of T, B and NK cells and are associated with lymphocyte activation. Given that altered immunity is an established risk factor for NHL, these results add to the biologic plausibility that TCE is a possible lymphomagen.

Characterization of Liver Injury Associated with Hypersensitive Skin Reactions Induced by Trichloroethylene in the Guinea Pig Maximization Test

Characterization of Liver Injury Associated with Hypersensitive Skin Reactions Induced by Trichloroethylene in the Guinea Pig Maximization Test: Xiaojiang Tang, et al. Guangdong Poison Control Center, China—Trichloroethylene (TCE) can induce non‐dose‐related hepatitis, possibly classified as delayed‐type hypersensitivity (immune‐mediated hepatitis), as well as dose‐related toxic liver injury. However, the difference in pathophysiology between the two kinds of hepatitis remains unknown. This study aimed to characterize the liver injury associated with hypersensitive skin reactions induced by TCE in guinea pigs. As a model of dose‐related acute toxic liver injury, the animals were treated with intradermal injection (ii) (0, 167, 500, 1500 or 4500 mg/kg of TCE) or dermal patch (dp) (0 or 900 mg/kg of TCE). The guinea pig maximization test (GPMT) was also carried out as a model of immune‐mediated liver injury, in which the total TCE dosage was below 340 mg/kg. In the group of TCE 4500 mg/kg (ii), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased (p<0.01), while total protein and globulin decreased (p<0.05). Evident fatty degeneration, hepatic sinusoid dilation and inflammatory cell infiltration were observed. No significant change was found in animals treated with TCE of doses below 500 mg/kg (ii) or 900 mg/kg (dp). In the GPMT, sensitization rates of TCE‐induced dermal allergy were 66%. ALT, AST, lactate dehydrogenase and the relative liver weight increased significantly (p<0.05) while albumin, IgA and γ‐glutamyl transpeptidase decreased significantly (p<0.05). Lesions of ballooning changes were observed in liver pathology. Thus, TCE could cause both acute‐type toxic liver injury and immune‐mediated liver injury, the so‐called delayed‐type hypersensitivity at doses below the dosage for toxic liver injury. Interestingly, the histopathological features were quite different: fatty degeneration was most prominent in the former, and ballooning in the latter.

Genetic polymorphisms of cytokine genes and risk for trichloroethylene-induced severe generalized dermatitis: A case-control study

Trichloroethylene (TCE)-induced severe generalized dermatitis (SGD) is considered to be a contact allergic disease and is dependent on a cell-mediated immune response. Little is known about its pathogenesis. Several lines of evidence suggest that tumour necrosis factor (TNF) and interleukin 4 (IL-4) are involved in the immunological and inflammatory reactions. To investigate the relation between polymorphisms of TNF and the IL-4 gene and the risk of TCE-induced SGD, a case-control study was conducted consisting of 111 patients diagnosed with SGD and 152 TCE-exposed workers without SGD. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the polymorphisms of TNF-α (G-238A, G-308A), TNF-β (intron 1) and IL-4 (C-590T). Logistic regression was applied to calculate the odds ratios (OR) and 95% confidence intervals. The results reveal that the frequency of TNF α-308 wild allele in cases was significantly higher than that in control subjects (p=0.049). Individuals with a heterozygous genotype of TNF α-308 were associated with the decreased risk of TCE-induced SGD relative to the homozygous genotype (OR=0.398, 95% CI=0.164–0.967). No significant differences in the allele and genotype frequencies could be demonstrated at any other polymorphic loci among both groups. The finding of a possible contribution of a TNF-α genetic polymorphism is a primary result because the pathogenesis of TCE-induced SGD is complex and likely to involve the interaction of a number of genes. A further study should be conducted to illustrate the influence of a link between certain relevant alleles in the assessment of genetic susceptibility.

Elevated urinary levels of kidney injury molecule-1 among Chinese factory workers exposed to trichloroethylene

Epidemiological studies suggest that trichloroethylene (TCE) exposure may be associated with renal cancer. The biological mechanisms involved are not exactly known although nephrotoxicity is believed to play a role. Studies on TCE nephrotoxicity among humans, however, have been largely inconsistent. We studied kidney toxicity in Chinese factory workers exposed to TCE using novel sensitive nephrotoxicity markers. Eighty healthy workers exposed to TCE and 45 comparable unexposed controls were included in the present analyses. Personal TCE exposure measurements were taken over a 2-week period before urine collection. Ninety-six percent of workers were exposed to TCE below the current US Occupational Safety and Health Administration permissible exposure limit (100 ppm 8h TWA), with a mean (SD) of 22.2 (35.9) ppm. Kidney injury molecule-1 (KIM-1) and Pi-glutathione S transferase (GST) alpha were elevated among the exposed subjects as compared with the unexposed controls with a strong exposure-response association between individual estimates of TCE exposure and KIM-1 (P < 0.0001). This is the first report to use a set of sensitive nephrotoxicity markers to study the possible effects of TCE on the kidneys. The findings suggest that at relatively low occupational exposure levels a toxic effect on the kidneys can be observed. This finding supports the biological plausibility of linking TCE exposure and renal cancer.

Chromosome-wide aneuploidy study of cultured circulating myeloid progenitor cells from workers occupationally exposed to formaldehyde

Formaldehyde (FA) is an economically important industrial chemical to which millions of people worldwide are exposed environmentally and occupationally. Recently, the International Agency for Cancer Research concluded that there is sufficient evidence that FA causes leukemia, particularly myeloid leukemia. To evaluate the biological plausibility of this association, we employed a chromosome-wide aneuploidy study approach, which allows the evaluation of aneuploidy and structural chromosome aberrations (SCAs) of all 24 chromosomes simultaneously, to analyze cultured myeloid progenitor cells from 29 workers exposed to relatively high levels of FA and 23 unexposed controls. We found statistically significant increases in the frequencies of monosomy, trisomy, tetrasomy and SCAs of multiple chromosomes in exposed workers compared with controls, with particularly notable effects for monosomy 1 [P = 6.02E-06, incidence rate ratio (IRR) = 2.31], monosomy 5 (P = 9.01E-06; IRR = 2.24), monosomy 7 (P = 1.57E-05; IRR = 2.17), trisomy 5 (P = 1.98E-05; IRR = 3.40) and SCAs of chromosome 5 (P = 0.024; IRR = 4.15). The detection of increased levels of monosomy 7 and SCAs of chromosome 5 is particularly relevant as they are frequently observed in acute myeloid leukemia. Our findings provide further evidence that leukemia-related cytogenetic changes can occur in the circulating myeloid progenitor cells of healthy workers exposed to FA, which may be a potential mechanism underlying FA-induced leukemogenesis.

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 formaldehydes 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.

High-resolution metabolomics of occupational exposure to trichloroethylene

Background: Occupational exposure to trichloroethylene (TCE) has been linked to adverse health outcomes including non-Hodgkin’s lymphoma and kidney and liver cancer; however, TCE’s mode of action for development of these diseases in humans is not well understood. Methods: Non-targeted metabolomics analysis of plasma obtained from 80 TCE-exposed workers [full shift exposure range of 0.4 to 230 parts-per-million of air (ppma)] and 95 matched controls were completed by ultra-high resolution mass spectrometry. Biological response to TCE exposure was determined using a metabolome-wide association study (MWAS) framework, with metabolic changes and plasma TCE metabolites evaluated by dose-response and pathway enrichment. Biological perturbations were then linked to immunological, renal and exposure molecular markers measured in the same population. Results: Metabolic features associated with TCE exposure included known TCE metabolites, unidentifiable chlorinated compounds and endogenous metabolites. Exposure resulted in a systemic response in endogenous metabolism, including disruption in purine catabolism and decreases in sulphur amino acid and bile acid biosynthesis pathways. Metabolite associations with TCE exposure included uric acid (β = 0.13, P-value = 3.6 × 10−5), glutamine (β = 0.08, P-value = 0.0013), cystine (β = 0.75, P-value = 0.0022), methylthioadenosine (β = −1.6, P-value = 0.0043), taurine (β = −2.4, P-value = 0.0011) and chenodeoxycholic acid (β = −1.3, P-value = 0.0039), which are consistent with known toxic effects of TCE, including immunosuppression, hepatotoxicity and nephrotoxicity. Correlation with additional exposure markers and physiological endpoints supported known disease associations. Conclusions: High-resolution metabolomics correlates measured occupational exposure to internal dose and metabolic response, providing insight into molecular mechanisms of exposure-related disease aetiology.

Comparison of hematological alterations and markers of B-cell activation in workers exposed to benzene, formaldehyde and trichloroethylene.

Benzene, formaldehyde (FA) and trichloroethylene (TCE) are ubiquitous chemicals in workplaces and the general environment. Benzene is an established myeloid leukemogen and probable lymphomagen. FA is classified as a myeloid leukemogen but has not been associated with non-Hodgkin lymphoma (NHL), whereas TCE has been associated with NHL but not myeloid leukemia. Epidemiologic associations between FA and myeloid leukemia, and between benzene, TCE and NHL are, however, still debated. Previously, we showed that these chemicals are associated with hematotoxicity in cross-sectional studies of factory workers in China, which included extensive personal monitoring and biological sample collection. Here, we compare and contrast patterns of hematotoxicity, monosomy 7 in myeloid progenitor cells (MPCs), and B-cell activation biomarkers across these studies to further evaluate possible mechanisms of action and consistency of effects with observed hematologic cancer risks. Workers exposed to benzene or FA, but not TCE, showed declines in cell types derived from MPCs, including granulocytes and platelets. Alterations in lymphoid cell types, including B cells and CD4+ T cells, and B-cell activation markers were apparent in workers exposed to benzene or TCE. Given that alterations in myeloid and lymphoid cell types are associated with hematological malignancies, our data provide biologic insight into the epidemiological evidence linking benzene and FA exposure with myeloid leukemia risk, and TCE and benzene exposure with NHL risk.

Alterations in serum immunoglobulin levels in workers occupationally exposed to trichloroethylene

Trichloroethylene (TCE) has been associated with a variety of immunotoxic effects and may be associated with an increased risk of non-Hodgkin lymphoma (NHL). Altered serum immunoglobulin (Ig) levels have been reported in NHL patients and in animals exposed to TCE. Recently, we reported that occupational exposure to TCE is associated with immunosuppressive effects and immune dysfunction, including suppression of B-cell counts and activation, even at relatively low levels. We hypothesized that TCE exposure would also affect Ig levels in humans. We measured serum levels of IgG, IgM and IgE, by enzyme-linked immunosorbent assay, in TCE-exposed workers (n = 80) and unexposed controls (n = 45), matched by age and gender, in a cross-sectional, molecular epidemiology study of occupational exposure to TCE in Guangdong, China. Exposed workers had about a 17.5% decline in serum levels of IgG compared with unexposed controls (P = 0.0002). Similarly, serum levels of IgM were reduced by about 38% in workers exposed to TCE compared with unexposed controls (P < 0.0001). Serum levels of both IgG and IgM were significantly decreased in workers exposed to TCE levels below 12 p.p.m., the median exposure level. Adjustment for B-cell counts had minimal impact on our findings. IgE levels were not significantly different between exposed and control subjects. These results provide further evidence that TCE is immunotoxic at relatively low exposure levels and provide additional biologic plausibility for the reported association of TCE with NHL.