This indicator measures the volume of aggregated consumption of toxic chemicals, expressed in million tonnes. The consumption of chemicals is calculated as the sum of the production volumes (PRODCOM) and the net import volumes of the chemicals (COMEXT) according to the equation: Consumption = production + imports – exports. The data on hazardous and non-hazardous chemicals show the total consumption of all chemicals. The two sub-categories of hazardous chemicals – hazardous to human health and hazardous to the environment – overlap by definition and as a result their sum is not equal to the total consumption of hazardous chemicals.