Dear Editor,

We were pleased to read the research article by H. Liu, et al. [1] which highlights the blood concentration of arsenic (As) can significantly predict the occurrence of preeclampsia (PE) and blood concentration of As may affect the occurrence of hypoproteinemia. This study provides important clues as to the prevention and treatment of PE. A number of studies found that a group of nutrients including macronutrients and micronutrients (e.g., calcium [2], iron [3, 4], magnesium [5], zinc [6], copper [7], and selenium [8], vitamins D [6], vitamins C, and vitamin E [9]) played a particularly important role in preeclampsia. However, the study only focused on the association between As exposure and PE. Thus, some questions still need further investigation.

There are many micronutrients and heavy metal that are associated with PE [10]. A retrospective cohort study found that blood lead levels had a nonlinear association with PE [11]. Another study also found that lower levels of vanadium might be associated with the development of PE [12]. Mixture analysis study provided evidence that exposure to multiple metals was associated with increased prevalence of PE, and the observed association with multiple metals was dominated by chromium and As [13]. However, the study not only explored the relationship between PE and pregnancy complications with blood concentration of As. Whether other heavy metals are associated with preeclampsia needs to be determined. Therefore, serum levels of common heavy metals should be measured.

Another problem of this study was that blood concentration of Asc as a predictor of preeclampsia is relatively arbitrary. It is well known that the greatest limitation of cross-sectional studies is the inability to make causal inferences, and this study is typical of case–control study. Another cross-sectional study found no association between arsenic exposure and risk of PE [14]. Large cohort studies and animal studies are necessary to determine the relationship between arsenic exposure and risk of PE.

Increasingly, exposure to environmental toxicants in air, soil, water, and household products was associated with risk factor of PE. Thus, environmental contaminants, specifically As, should be measured to explore the relationship between PE and environmental concentration of As. Preeclampsia is the most common pregnancy complications and is the leading cause of maternal and fetal morbidity and mortality worldwide. Defining acceptable As concentration thresholds for pregnant women in the setting of varied exposure environments will assist in identifying the populations at risk.

Conclusion

Overall, this was an observational study, and thus, we can only report association rather than infer causation. Large-scale cohort studies and animal studies are necessary to establish a causal relationship between As exposure and PE. In addition, this study did not examine whether other heavy metals are associated with PE.