Introduction

There has been a disproportionate amount of attention by environmentalists - and regulatory bodies - to controlling pollutant emissions from manufacturing processes.) However, manufacturing processes- beyond the extraction (mining) and ore beneficiation stage are much less important sources of pollutant emissions than postmanufacturing consumption activities. This is true at least for several of the most toxic heavy metals. In six of seven cases for which reasonable historical data can be cited, the consumption contribution to total mobile emissions is growing; in three of seven cases it is close to 100 per cent of total mobile emissions.

In this context, consumption means dissipative use. It is not restricted to use by "final consumers" in the usual economic classification. In fact, toxic metal emissions from manufacturing activities are mostly due to intermediate consumptive uses of metallic compounds such as catalysts, fuel or lubricant additives, detergents, pigments, pesticides, preservatives, germicides, fungicides, and so on. The major exception is trace metals in fly ash from coal combustion and fertilizer.

An historical reconstruction of US emissions of toxic heavy metals to the environment, resulting from dissipative consumptive uses, is presented in this chapter. The major implication of this exercise could be to confirm, in quantitative terms, the following assertion: that dissipative (intermediate and final) uses of heavy metals account for more waste residuals than losses from manufacturing processes per se. This statement would seem self-evident for "minor" metals such as arsenic, cadmium, and mercury, which have few, if any, uses that would permit recycling. However, it is also true for lead and zinc, at least in the past. Only in the cases of silver, chromium, and copper, whose chemical applications are outweighed by metallic and structural applications, is the matter in doubt.

The eight metals are considered hereafter as a single natural group, not only because of their toxicity, but because of the complex interrelationships in their production and uses. All except chromium are obtained from sulphide ores. Arsenic is a by-product of copper ores (and is also found in iron ores and phosphate rocks); cadmium is a by-product of zinc ore; silver is a by-product of copper, zinc, and lead ores; and copper, zinc, and lead are all contaminants of each other's ores.

On the use side, arsenic, copper, chromium, lead, and mercury have major overlapping and competing pesticidal, fungicidal, and bactericidal uses; lead, cadmium, chromium, and zinc have major overlapping uses as pigments; cadmium, chromium, and zinc have overlapping and competing uses in metal plating; cadmium, mercury, zinc, and silver are all used in electric batteries, and so on.