Bottled, tap, and filtered drinking water associated health impacts and carbon footprint: A modelling study in Barcelona, Spain

Nitrate and trihalomethanes are widespread chemicals in drinking water associated with colorectal and bladder cancer, respectively. Drinking water choices determine different exposure levels and environmental impacts. We assessed and compared health impacts and carbon footprint of drinking water options in Barcelona, Spain. Drinking water habits, trihalomethane and nitrate concentrations, and estimated disability adjusted life years (DALYs) of bladder and colorectal cancer in Barcelona were obtained. We defined 5 scenarios: (S1) current drinking water habits; hypothetical situations where everyone drinks (S2) tap water, (S3) bottled water, (S4) reverse osmosis-RO filtered water, and (S5) active carbon filtered water. Bladder cancer population fraction attributable to trihalomethanes and colorectal cancer attributable to nitrate was estimated for the different scenarios using published exposure-response functions. The total set of greenhouse gas emissions (CO2-equivalent Kg) generated by materials flow, energy resources, transportation, and waste disposal were calculated. Bottled water was the most used choice (52%), and the “all bottled water” scenario led to the highest carbon footprint. The “all filtered-RO” scenario yielded the lowest DALYs and “all tap water” yielded the lowest carbon footprint. Domestic filters may offer a compromise between health and environmental awareness in drinking water behavior that warrants future research. This study highlights how a combined approach of Health Impact Assessment and Carbon Footprint can be used to evaluate risks of different chemicals found in drinking water (trihalomethanes and nitrates) through various water consumption scenarios (including current one, all tap, bottled, filtered with reverse osmosis and active carbon). By incorporating environmental and health data into an urban context (Barcelona), this methodology substantiates the need for decision-making based on robust findings on both public health impacts and sustainability trade-offs for future policies. These findings underscore the significance of the drinking water choices in the community heavily depending on bottled water.