Arsenic exposure

We calculated two exposures for each cohort member. The first was a time-weighted average exposure, calculated as the arsenic concentration in drinking-water multiplied by the time lived at each address, summed for all residential addresses during the study period and divided by the total observation time, with the unit micrograms per liter (Equation 1).

Second, we calculated the cumulated arsenic exposure by cumulating the products of “arsenic level × time” for each address occupied during the total observation period and multiplied by the total daily intake of tap water, with the unit milligram (Equation 2). The total daily intake of tap water was calculated as the sum of intake of tap water, coffee, tea, and fruit syrup diluted with tap water, which was reported at enrollment into the cohort.