100 Years of Advancement
In 2007, the Journal of the Air and Waste Management Association (JAWMA) published over 1,500 pages of research findings. Although the science of measuring and controlling air pollution has seen phenomenal advancements since 1967 when the journal (then called JAPCA) began publishing peer-reviewed works, 21st-century IH readers might find some of the older articles still compelling today: “Concepts of Electric Arc Furnace Fume Control” (1968); “Operating Experience with a Large Baghouse in an Electric Arc Furnace Steelmaking Shop” (1970); and “Blast Furnace Casthouse Control Technology” (1981).
Among the 2007 collection of published articles was one from the University of California, Davis on emissions from stainless- and mild-steel welding. Using new experimental techniques, the group confirmed (approximately) the EPA’s prior AP-42 data for hexavalent chrome, Cr(VI), emissions from stick and gas welding (using ~18% chromium electrodes) to be approximately 0.2 and 0.02 g Cr(VI)/kg of electrode, respectively, and found Cr(VI) to be undetectable during welding of mild steel (with chrome-free electrodes). These findings are of interest for public and occupational health because inhalation exposure to high concentrations of Cr(VI) in certain industries has been associated with an increased risk of lung cancer.
Another article that might interest IH readers is about encapsulation of metals in slag. The study addressed the vitrification of municipal solid waste (MSW) incinerator ash as a means of reducing dioxins, recovering metals that are volatile at high temperatures (Cd, Pb, Zn), and encapsulating non-volatile metals (Cr, Cu, Ni) – thus reducing their atmospheric mobility. The authors found that slags higher in SiO2 contained greater amorphous volume fractions. These slags were more resistant to acid leaching of the metals, which also reduces their environmental mobility in landfill or similar applications.
Brick kilns in northern Mexico were the focus of an article from researchers at New Mexico State Univestity (NMSU) and Universidad Autonoma de Ciudad Juarez. Traditionally in this region, open-top, scrap-wood-fueled kilns would be used to fire batches of up to 6,000 bricks. Emissions of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH) were unabated and high. NMSU researchers implemented improvements wherein two adjacent kilns were covered and interconnected. The pair of kilns was operated in tandem, with a fired kiln exhausting through its unfired but loaded twin, thus burning and/or trapping PM and PAH. Expectedly, the greater environmental benefit was attributed to covering the kilns, which increased soot particle burnout. The interconnection led to operational difficulties, including flow oscillations and poor natural draft.
An article from researchers in Taiwan discussed how a process used to treat electric-arc-furnace fly ash appeared to be increasing the dioxin risk instead of reducing it. The study examined input and output dioxin from a “Waelz rotary-kiln” EAF fly-ash-treatment process and found that although the process reduced the total mass of dioxins by ~38%, it actually increased the total equivalent toxicity of the emitted dioxins by ~19% due to chlorine atom redistribution.
Probably the most interesting material for history buffs is a pair of review articles that appeared in the June 2007 issue. A former EPA associate director and the AWMA Review Committee put together perspectives (with 285 citations) on air quality during the organization’s first hundred years.[5,6] The century was divided into periods based on the focus of the abatement efforts: the “smoke era” (1900-1950); the foundation of Air Quality Management (1950-1960); the pre-EPA period (1960-1970); and the National Ambient Air Quality Standards era (1971-present). The authors hailed the discovery of the photochemical smog cycle in the 1950s as well as the absolute reductions in air emissions that have occurred concurrently with increases in population, energy consumption and gross domestic product from the 1970s forward. Other topics of interest include health effects, regional haze, acid rain, air toxics and emissions trading. A worthy read for all. IH