Association of urinary arsenic concentrations with inflammation: overall and by folate intake, body mass index, and gender

Background

Inorganic arsenic (iA) exposure is associated with increased risk of lung, bladder, and skin cancer, as well as cardiovascular disease and diabetes. C-reactive protein (CRP), a measurement of inflammation, has been associated with these conditions. As the relationship between urinary arsenic and CRP remains unclear, we aim to determine if there is an association and to examine effect modification by dietary and lifestyle factors.

Methods

The study includes 5761 adults, ages 25+, over four survey cycles (2005–2006, 2007–2008, 2009–2010, and 2015–2016), surveyed as part of the National Health and Nutrition Examination Survey (NHANES) and included in the laboratory subsample. Survey-weighted multivariable linear regression was used to determine the association between log-transformed arsenic concentrations ($\sum As$, monomethylarsonate [MMA], and dimethylarsinate [DMA], and primary and secondary methylation indices [PMI, SMI]) and log-transformed CRP. Models were stratified by gender, body mass index (BMI), folic acid supplement use, and dietary folate intake.

Results

Three forms of urinary arsenic were associated with statistically significant lower levels of CRP ($\sum As$: −3.06 %, MMA: −2.34 %, DMA: −2.10 %, per 25 % increase in arsenic concentration). The association between SMI and CRP varied by gender (p-interaction: <0.01) and dietary folate intake (p-interaction: 0.04).

Conclusions

The inverse association between urinary arsenic concentrations and CRP was unexpected, highlighting a need to better characterize effects of iAs at low levels of exposure. Effect modification by dietary folate intake suggests that folate may affect the secondary methylation pathway, however, more research is needed to understand the role that folic acid plays in arsenic methylation.