Chapter 8 - Industrial Emissions and Controls
Emissions of lead, together with other harmful or potentially hazardous substances, can occur at all stages of production, from mining of ore, during smelting and refining, and also, potentially, during the manufacture of the finished products. Lead emissions also occur from non-related industries, such as other metal works, incinerators and in, small amounts, from power stations. The quantities of emissions are declining in the Western World as environmental legislation reduces permitted releases, increasingly effective pollution abatement technologies are used, and industry moves gradually towards inherently cleaner, more efficient technologies. However, some emissions are inevitable, especially from older plants which process many thousands of tonnes of material per year. However, the requirement to use Best Available Techniques under forthcoming IPPC legislation will further reduce emissions from older plants.
The bulk of emissions are in the form of solid wastes; a much smaller amount is emitted to air, and less still to water. The form of the emissions determines their likely mobility, bioavailability and potential to reach and affect a target ecosystem or human population. Other important factors are whether the emissions are part of controlled, measured releases, uncontrolled fugitive emissions, or resulting from a plant incident.
Despite the recognition of historical environmental damage and health effects in the work force connected with the lead industry over many centuries, it is only in the past hundred or so years that effective control measures began to be implemented, both to protect the health of workers and to reduce pollution. Good plant design, with reduction of the potential for the emission of contaminating substances, is of paramount importance, and the newer smelting processes are inherently much cleaner than traditional blast furnaces. Pollution abatement technologies, including the treatment of exhaust gases and liquid effluents to remove a proportion of the metal content, have also significantly reduced emissions. Other general measures to improve the cleanliness of sites are implemented to varying degrees. These measures, taken together, have considerably reduced emissions.
Throughout the Western World, factories are legally required to operate within the limits on discharges set by their regulatory authority, although not all emissions are continuously monitored. In this respect, many plants in the EU have some form of perimeter monitoring. There are inherent problems in measuring fugitive emissions, such as windblown dusts, can be addressed by monitoring air quality within and at the perimeter of the site and modelling the results. In general it is difficult to estimate the percentage of the emission arising from fugitive sources. In certain countries allowable discharges are set individually for each plant.
There are legal limits and recommended guidelines for concentrations of lead in air outside plants, and monitoring is usually practised. Sites with the highest concentrations of lead in air are in the vicinity of industrial locations. Compliance with the former EU standard of 2mg/m3 is now virtually universal, though there are still a few sites which exceed the new standard and the WHO guideline value of 0.5mg/m3.
Those mostly exposed to releases within the plant are the workforce. Before industrial controls were introduced around the turn of the century, lead poisoning was common in foundry workers, and was also found in other trades which used lead. The implementation of controls such as maintaining minimum standards of air quality within the works, medical surveillance of employees, use of protective equipment, and provision of conditions of good hygiene in general, have made excessive occupational lead exposure a rare occurrence.
Outside the Western World, control measures are not always enforced to the same degree and there are still undoubtedly many cases of high occupational exposure to lead and environmental damage resulting from industrial emissions in the developing world.
In short, while it is important to recognize the huge improvements made by industry in recent decades, there are considerable variations between standards in the developed and the developing world. Emissions from some plants outside the EU continue to contribute towards elevated exposure of local residents, and high lead levels in soils leave a legacy for centuries. It is therefore important to continue to work toward implementation of best practice, and to aim for a level of emission that is globally sustainable.
