Review of the potential health effects associated with particle emissions from gas-fired glass furnaces

Rates of particle emission from glass furnaces exceed those allowed under the relevant process guidance note. The emitted particles, however, are largely composed of sodium sulphate, which being highly soluble and already present dissolved form in blood and tissue, would not be expected to have a substantial effect on the respiratory health of exposed individuals. This independent review was undertaken to assess the potential health effects that might be associated with particle emissions from gas-fired glass furnaces. Dispersion modelling suggests that both short and long term increments in local concentrations of airborne particles associated with emissions from glassworks are small in comparison the UK’s air quality objectives. Increments in the concentrations of specific toxic components of the waste gas dust including heavy metals and silica are extremely small in comparison to recognised “”safe”” levels of exposure. Emissions of sulphur dioxide, however, may give rise to a small increase in local levels of aerosol acidity and emissions of nitrogen oxides may give rise to occasional excedences of the one hour nitrogen dioxide air quality standard. There is relatively little information available about the potential toxic effects of exposure to airborne sodium sulphate. Experimental results suggest that the toxicity of inhaled sulphate salts varies with their acidity. Fine particles of sodium sulphate are likely to be less biologically active than the more acid sulphates typically present in urban aerosol. The transition metals content of ambient urban PM10 may play an important role in promoting oxidative damage to the airways. The transition metals content of emissions from glass works is generally smaller than that of ambient PM10 and may also be less bioavailable as most of the metals present are locked up in glass. Epidemiological studies have suggested an association between ambient concentrations of airborne sulphate and a range of health endpoints. It seems likely, however, that sulphate in these studies is acting as a marker for some other more toxicologically relevant component of airborne particulate. There is more consistent evidence that aerosol acidity may have an independent effect from that of particles more generally. Overall, it seems likely that primary particle emissions from gas-fired glass furnaces have a lower toxicity per unit mass than typical urban PM10. The formation of secondary acid aerosol under conditions of particularly unfavourable dispersion may occasionally, however, give rise to a small increase in respiratory symptoms in the local area. There would be a greater environmental benefit in cutting emissions of sulphur dioxide and nitrogen oxides than in cutting particle emissions. “”