Microplastic exposure disparities in California communities through bottled water consumption

Abstract Increasingly, governmental agencies are taking action in response to health concerns associated with microplastic exposure in drinking water. These efforts have focused primarily on municipal tap water rather than bottled water. This is concerning, given the surge in bottled water consumption in the U.S., a surge partially fueled by negative perceptions of tap water quality, especially among minority communities. Even though microplastics may not be the biggest health risk or primary reason for consumer choices around tap and bottled water, the rising concerns around microplastic exposure and impacts on human health are important to take into consideration. A systematic review was conducted to assess microplastic concentrations in various sources of drinking water, including bottled water and municipal tap water. To facilitate a more accurate comparison of microplastic concentrations between studies, we realigned the analyzed microplastic size classes between studies. Additionally, trends in California household-level bottled water purchases were analyzed using a nationwide dataset of bottled water transactions to determine the corresponding rates of microplastic exposure associated with these consumption patterns. Our results suggest that there is a sevenfold higher concentration of microplastics in bottled water compared to tap water globally. In comparison, studies conducted in the Global North have found a six times higher concentration of microplastics in bottled water compared to tap water, and seven times more microplastics in bottled water compared to tap water in the Global South. While income is found to be positively associated with bottled water purchases and increases in microplastic exposure in California, substantial disparities in exposure persist by ethnicity and race after controlling for income. Although microplastics may not be the primary health risk or the primary reason for consumer choices regarding tap and bottled water, the growing concerns about microplastic exposure and its impacts on human health are important to consider. Choices made by consumers regarding drinking water types, regardless of the reason for these choices, should be made with the best available information. Therefore, our results underscore the importance of addressing information disparities related to bottled water quality. This is particularly important within marginalized communities served by high-quality municipal drinking water, where misperceptions of tap water quality and limited information on bottled water quality contribute to the consumption of bottled water.