Mercury Inhalation Risks from Use of CoalCombustion Products(CCPs)as Structural Filland from Disposal of CCP-Containing Wallboardand Concrete in Landfills

摘要

The beneficial use of coal combustion products(CCPs)conserves natural resources,reduces landfill waste,and can improve the quality and performance of construction materials.Concerns remain,however,about potential exposures to mercury(Hg)in CCPs,including coalfly ash(CFA)used in concrete and structural fills,as well as flue gas desulfurization(FGD)materials used in wallboard.Moreover,with continued regulation of airborne Hg emissions,Hgconcentrations in CCPs are likely to increase.Therefore,to examine potential exposures to Hgemissions from CCPs and any associated human health risks,we conducted a riskassessment to determine worst-case inhalation and more typical exposures to Hg for twooutdoor exposure scenarios:(1)CFA used as structural fill material,and(2)CCP concrete andwallboard disposed of in a construction&demolition(C&D)landfill.For the structural fillscenario,we considered both fugitive dust emissions and volatilization of elemental Hg from theCFA.For the landfill scenario,we considered volatilization of elemental Hg from CCPs inconcrete and wallboard.We estimated outdoor Hg air concentrations using the USEnvironmental Protection Agency's Wind Erosion SCREEN3 models,applying conservative,worst-case assumptions.To estimate potential risks to children and adults,we adjustedmodeled outdoor air concentrations for exposure time,frequency and duration and compared totoxicity criteria.Our results showed that Hg exposures via inhalation from the CCP materialsare near or below ambient Hg levels,and several orders of magnitude lower than health-basedtoxicity criteria.Thus,our findings indicate that upper-end exposures to Hg from the beneficialuse of CCPs in structural fills,and from disposal of building materials containing CCPs,are notexpected to pose an inhalation health risk.Key results are displayed graphically below.