Human exposure to concerning substances such as lead has decreased in Flanders over the past twenty years. For arsenic or certain insecticides, exposure has stagnated. For part of the Flemish population, levels of some metals, pesticides, and PFAS exceed the safe exposure threshold. The lower the exposure, the smaller the risk of adverse health effects. By 2050, the risk posed by concerning substances must be acceptable for humans and the environment. Exposure varies by location and individual. For half of the measured substance groups, exposure is linked to education or income. Human biomonitoring — measuring in humans — is essential to support and adjust policies on concerning substances.