Environmental health is a subset of public health that focuses on people's relationships with their surroundings, improves human health and well-being, and builds healthy and secure communities. Any complete public health system must include environmental health. To protect people and provide communities with healthier settings, the field seeks to improve policies and programmes that decrease chemical and other environmental exposures in air, water, soil, and food. A healthier environment could prevent about a quarter of the world's illness burden. The COVID-19 pandemic serves as a further reminder of the delicate balance that exists between humans and the environment.