Pollution is the presence of foreign substances/energies and their adverse impact on human health, environment and living organisms. It is one of the triple planetary crises alongside climate change and biodiversity loss. Pollution can take many forms including contaminated water, air, soil, and food. Pollution affects everyone but disproportionately harms poor people. This is because of their lower socioeconomic status and greater vulnerability to its effects. Pollution is linked to debilitating and deadly diseases like asthma, lung cancer and heart disease. It also results in low productivity, high healthcare costs and economic losses, and reduces life expectancy.

Air pollution is a mix of gases and particles that include ground-level ozone (often referred to as smog), carbon monoxide, various forms of nitrogen oxides, sulfur oxides, volatile organic compounds, polycyclic aromatic hydrocarbons and fine particulate matter. It is produced when hazardous materials emitted by vehicles, factories and power plants re-combine with sunlight in the atmosphere. Natural sources of air pollutants include forest fires; ash and fumes from volcanic eruptions; and emissions from wetlands and decomposing organic material.

Exposure to air pollutants can have a range of short- and long-term impacts on animal health and wellbeing. They can lead to reproductive and developmental problems; cause respiratory infections; and affect cardiovascular, nervous and immune systems. Persistent toxic chemicals can biomagnify up the food chain, causing harm at higher levels of the ecosystem. The destruction of habitats by humans also contributes to wildlife deaths and reduced biodiversity.