Correlation between arsenic methylation metabolism and skin and liver damage in patients with coal-burning arsenism

  Objective  To analyze the level of urinary arsenic methylation metabolism and its correlation with skin and liver damage among coal-burning arsenism patients.

  Methods  Based on the “Diagnostic Criteria of Endemic Arsenism” (WS/T 211 — 2015) issued by Health and Family Planning Commission of the People′s Republic of China, we recruited 202 arsenism patients in an endemic area with arsenic pollution caused by coal-burning in southwestern region of Guizhou province and subdivided the patients into a mild (n = 48), moderate (n = 70) and severe group (n = 84) according to the severity of skin damage of the patients. The controls of the study were 56 healthy residents recruited in a region 12 kilometers away from the endemic arsenism area and the controls had everyday life similar to that of patients and no history of exposure to burning high arsenic coal. Serum albumin (ALB) and albumin/globulin (A/G) ratio were used to assess liver damage of the participants. High performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) was adopted to detect trivalent arsenic (As³⁺), pentavalent arsenic (As⁵⁺), monomethyl arsenic (MMA) and dimethyl arsenic (DMA) in the urine samples of the participants and the detection results were used to calculate total arsenic (tAS), proportions of As³⁺, As⁵⁺, MMA and DMA (As³⁺%, As⁵⁺%, MMA% and DMA%), primary methylation index (PMI), and the secondary methylation index (SMI).

  Results  Compared to the controls, the arsenism patients had significantly increased urinary As³⁺, MMA, As³⁺% and MMA% (P < 0.05 for all) but decreased DMA%, PMI and SMI (all P < 0.05). The patients′ urinary As³⁺% and MMA% increased and SMI decreased significantly with the severity of skin damage (P < 0.05 for all). In the arsenism patients, the serum ALB and A/G decreased significantly in comparison with those in the controls (both P < 0.05); the serum ALB declined with the increase of urinary As³⁺% and MMA% and the decrease of urinary DMA%, PMI and SMI (all P < 0.05), while with the increase of urinary As³⁺% the serum A/G declined significantly (P < 0.05). When used as two indicators for the assessment of arsenism, the urinary As³⁺% and MMA% presented the area under the receiver operating characteristic curve (AUC) of 0.84 and 0.63 and the optimal cutoff point of 14.37% and 12.10%; the specificity of the two cutoff points were 83.93% and 73.21% and the sensitivity of the two cutoff points were 73.27% and 50.99%. When combining As³⁺% and MMA% as an integrated indicator, the indicator′s AUC was 0.82, with a specificity of 89.29% and a sensitivity of 66.83%, respectively.

  Conclusion  Attenuated arsenic methylation metabolism is a risk factor for skin and liver damage among coal-burning arsenism patients. Urinary As³⁺% and MMA% could be used as potential indicators for the assessment of coal-burning arsenism and the assessment specificity increases when the two indicators being combined.