Fly Ash - Exposure Concerns

Exposure Concerns

Crystalline silica and lime along with toxic chemicals are among the exposure concerns. Although industry has claimed that fly ash is "neither toxic nor poisonous," this is disputed. Exposure to fly ash through skin contact, inhalation of fine particle dust and drinking water may well present health risks. The National Academy of Sciences noted in 2007 that "the presence of high contaminant levels in many CCR (coal combustion residue) leachates may create human health and ecological concerns".

Fine crystalline silica present in fly ash has been linked with lung damage, in particular silicosis. OSHA allows 0.10 mg/m3, (one ten-thousandth of a gram per cubic meter of air).

Another fly ash component of some concern is lime (CaO). This chemical reacts with water (H₂O) to form calcium hydroxide, giving fly ash a pH somewhere between 10 and 12, a medium to strong base. This can also cause lung damage if present in sufficient quantities.

In a study by NIOSH at a cement company, crystalline silica exposures from fly ash were determined to be of no concern. For maintaining a safe workplace emphasis must be placed on maintaining low nuisance dust levels and to use the appropriate personal protective equipment (PPE). The conclusion of this NIOSH study is supported by other studies devoted to the effects of fly ash on the health of workers in power plants. According to these studies, fly ash dust should not be considered as "silicotic dust", because most of the crystalline silica is coated by amorphic alumino-silicates (glass), the main constituent of fly ash particles. This was shown particularly on the basis of scanning electron microscopy observations, by a research work performed in the Netherlands, but similar findings were obtained also in other countries.