Geology

Organic chemistry

Hazard

Aquifer

Groundwater

Biology

Contamination

Arsenic contamination of groundwater

Chemistry

Geotechnical engineering

Ecology

Environmental hazard

Arsenic

Environmental remediation

Water resource management

Contaminated groundwater

Environmental science

Science

Dowsing for danger Arsenic is a metabolic poison that is present in minute quantities in most rock materials and, under certain natural conditions, can accumulate in aquifers and cause adverse health effects. Podgorski and Berg used measurements of arsenic in groundwater from ∼80 previous studies to train a machine-learning model with globally continuous predictor variables, including climate, soil, and topography (see the Perspective by Zheng). The output global map reveals the potential for hazard from arsenic contamination in groundwater, even in many places where there are sparse or no reported measurements. The highest-risk regions include areas of southern and central Asia and South America. Understanding arsenic hazard is especially essential in areas facing current or future water insecurity. Science , this issue p. 845 ; see also p. 818

Global threat of arsenic in groundwater