Exposures through drinking water and risk of chronic disease

Abstract

Drinking water is the most important constituent of our diet. Yet, the importance of drinking water quality for population health is understudied. The overall aim of this thesis was to increase this knowledge by examining the relationship between some widespread waterborne exposures with the incidence of several chronic conditions, each with a high global disease burden.

In paper I, we estimated the exposure to fluoride through both diet and drinking water as well as measured fluoride in urine from 4,306 women enrolled in a population-based cohort. We assessed the association of each exposure with bone mineral density (BMD) and incidence of fractures and found that both were associated with higher BMD but also increased risk of hip fractures, suggesting denser but more brittle bone.

In paper II, we assessed the exposure to drinking water calcium and magnesium in 26,733 women in a population-based cohort using information on residential history from registers in combination with monitoring data from a national drinking water database. We prospectively assessed the association of a combined exposure to calcium and magnesium, as well as each of the minerals with incidence of myocardial infarction and stroke and found that the women with the highest combined exposure and with the highest magnesium exposure had a lower risk of stroke.

In paper III and IV, we estimated the exposure to drinking water trihalomethanes (THM), which are the most prevalent disinfection by-products formed in chlorinated water, in 58,602 men and women in two population-based cohorts using data on residential history and drinking water monitoring data. While we in paper III found no overall association with bladder cancer, we in paper IV observed an increased risk of proximal colon cancer in men with the highest exposure to THM.

In paper V, we reviewed the epidemiological evidence of exposure to residential drinking water concentrations of THM with risk of cancer using a systematic review and dose-response meta-analysis approach. We found that TMH were associated with increased risk of both bladder cancer and colorectal cancer, mainly in men. Most studies included were judged to have moderate risk of bias, and the overall strength of the evidence was concluded to be limited-suggestive for increased risk of bladder cancer and colorectal cancer.

In summary, the five constituent papers in this thesis provide important insight to the relationship between several waterborne exposures that are widespread in drinking water and population health. The results may help guiding future recommendations and regulations on drinking water quality that better protect human health.