In 2020, 2 billion people lacked access to uncontaminated water, while 771 million lacked basic sanitation services, primarily in sub-Saharan Africa and rural areas . Even in high-income countries, poor-quality drinking water can be a health issue . For example, in a sampled population in Canada, reported exposure to exposure routes for waterborne illness included 7% from private wells and 71.8% from municipal water . Drinking water treatment can be compromised by degraded source water quality and extreme weather events, including droughts, storms, ice storms and wildfires that overwhelm or cause infrastructure damage  . Adverse health effects are exacerbated due to the absence of adequate WaSH, particularly in poorer households , WaSH infrastructure failure  or inadequate WaSH facilities in emergency shelters . For example, WaSH coverage decreased from 65% to 51% due to damage from floods and earthquakes in Malawi . Loss of electricity also impacts WaSH service delivery , and infrastructure damage caused by climate hazards may reverse progress on universal access to WaSH  . In addition, wastewater outflows have been associated with a 13% increased relative risk of gastrointestinal illness through contaminated drinking water sources  . Harmful algal blooms represent an emerging health risk, but lack of monitoring and reporting prevent risk exposure assessments  . Chemical contaminants  have been linked to non-communicable diseases, including neurological disorders, liver and kidney damage, and cancers , and to some water-related diseases  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report