Production-related heavy metal emissions

Production processes for heavy metals, for our purposes, begin with smelting and refining. We do not include mining per se, or associated ore concentration (beneficiation) processes, which are normally carried out near the mine. While these processes generate enormous quantities of waste material, they are normally carried out in fairly remote locations.

In principle, we also include secondary refining in this category. In addition, trace metals are emitted in significant quantities via fly ash from the combustion of coal, oil (especially residual oil), and possibly wood. Though fuels are utilized for residential heating and transportation, as well as for utility and industrial purposes, we class fuel combustion as part of the production of housing and transport services. Thus, all emissions of heavy metals associated with fly ash from fossil-fuel refining are considered to be production-related. On the other hand, we include lead additives to gasoline and zinc additives to lubricating oil as consumption-related.

It must be pointed out that incineration of refuse and sewage sludge also results in heavy metal emissions. But this is an environmental transfer, not a true source of metallic pollutants. All of the metals emitted by incinerators must have been originally embodied in items of consumption discharged as wastes. Incinerator wastes are therefore consumption-related. Data on incinerator emissions are relevant to the extent that they provide evidence of final disposal routes.

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