Thursday, 9 August 2012

Why are mineral workers warned of the dangers of RCS but not local residents?

Respirable Crystalline Silica is invisibly fine dust generated when quarrying and processing sand and gravel. Aggregate Industries' staff at Blackhill Quarry are warned of its dangers, as are at-risk workers elsewhere.

Report on Carcinogens by the US Health Department warns "Residents near quarries and sand and gravel operations potentially are exposed to respirable crystalline silica." Another report concludes "In our study, there seems to be a risk also in groups exposed to lower levels [of respirable quartz]. There is no consensus how low an acceptable risk level ought to be."

The deposits of sand and gravel at Straitgate are made of quartzite - a crystalline form of silicon dioxide or silica. Respirable Crystalline Silica (RCS) is angular Particulate Matter less than 10μm in size (PM10) that can enter the lungs. The quarrying sector is a major producer of PM10. The Health Protection Agency advises "The distance travelled by dust emissions will depend on the particle size and on the wind speed and turbulence. Smaller dust particles will stay airborne for longer and disperse over a wider area. Strong and turbulent winds will also keep larger particles airborne for longer. Data reported from quarries indicated that the courser dust particles (>30μm) are mainly deposited within 100m of the source, intermediate particles (10-30μm) between 250 and 500m, while fine particles (<10μm) can travel up to 1 km (DoE, 1995a,b). Ultrafine particles (<2.5μm) would be expected to travel considerably further." 

RCS can be generated a number of ways (not just from processing). "Inhaling finely divided crystalline silica dust in very small quantities over time can lead to silicosis, bronchitis, or cancer, as the dust becomes lodged in the lungs and continuously irritates them, reducing lung capacities. (In the body crystalline silica particles do not dissolve over clinically relevant periods of time.) Children, asthmatics of any age, allergy sufferers, and the elderly (all of whom have reduced lung capacity) can be affected in much less time." In its most common form, chronic silicosis "Usually [results] from long-term exposure (10 years or more) to relatively low concentrations of silica dust and usually appearing 10–30 years after first exposure."

The American Lung Association writes "...public concern may be raised about potential health effects from brief exposure to airborne silica or residence in locations where prevailing winds carry silica particles from natural or industrial sites. There is little evidence to suggest that brief or casual exposure [would living near a quarry be "brief or casual"?] to low levels of crystalline silica dust produces clinically significant lung disease or other adverse health effects. Chronic simple silicosis has, however, been described after environmental exposures to silica in regions where soil silica content is high and dust storms are common."

The Health and Safety Executive (HSE) advises (guidance sheets QY0 and QY2) "All RCS is hazardous". "Tell workers: that very fine quarry dust can cause silicosis, which leads to disablement and early death". The HSE adds, with regard to construction sites, "In 2006, the workplace exposure limit for RCS was reduced to 100μg/m3 and there is pressure to lower it further to 50μg/m3 as epidemiological data suggest there is no known level of exposure at which silicosis does not occur." "Whilst we are able to estimate the exposure to RCS of an individual at work from past data, little is known about the inadvertent exposure of people who are close to but not involved in the work activity". HSE measurements did however "indicate the migration of silica across sites and potentially beyond the site boundaries". As far as recorded cases go, the HSE maintains "No cases of silicosis have been documented among members of the general public in Great Britain, indicating that environmental exposures to silica dust are not sufficiently high to cause this occupational disease". However "It should also be noted that excessive long term exposures to almost any dust, are likely to lead to respiratory (breathing) problems." HSE's American equivalent, the OSHA, warns "If it’s silica, it’s not just dust".

Aggregate Industries warns about RCS, but what warnings has DCC given? Well, no mention at all of RCS. Its Sustainability Appraisal did warn "Due to a changing climate there is the potential for the impact of noise and dust on sensitive receptors to become more intense. Hotter summers will provide conditions that will produce additional dust, and people will spend more time outdoors and leave the windows of dwellings and workplaces open for longer." "There is likely to be a negative impact upon the well-being and health of the residents at Straitgate Farm. This impact, combined with those likely for low to medium sensitive properties in the vicinity, would lead to a significant negative impact during the working of minerals". Its recommendation? "Policy relating to dust could encourage screening measures and dust control/mitigation". In its current Minerals Plan DCC "...will consider the practicality and the cost of methods of environmental control such as the spraying of materials with water at suitable stages in their handling and transport, the watering of areas of the site regularly used by vehicles and the use of dust extractors." Are the phrases "could encourage" and "consider the practicality and the cost" enough? RCS is carcinogenic. Cllr. John Hart, Leader of DCC, reiterated recently "you have to extract minerals from where they were deposited" - but to the detriment of human health? DCC's slogan is, after all, "improving life for all".

How much protection would residents expect from this carcinogenic dust source? Planning4Minerals (P4M) stresses that "Prevention of dust generation is critical [for example by working the mineral wet and damping internal haul roads] - once in the open air ...the operator will have little or no control over where [dust] settling occurs." P4M expects the "use of buffer zones to isolate dust sources from surrounding communities, often incorporated into local planning policy, with distances of 250-500m typically adopted, unless there are unusual or exceptional reasons to permit a variation." However, one study "monitored silica concentrations ...near a sand and gravel facility in Central California" and found "the impact from this source was still evident, even at the furthest downwind monitor - 745 meters away". The Technical Guidance to the NPPF says "A dust assessment study should be undertaken..." and "...additional measures to control PM10 might be necessary if, within a site, the actual source of emission (e.g. the haul roads, crushers, stockpiles etc.) is within 1,000m of any residential property or other sensitive use". Dust monitoring would form part of the planning conditions for any new quarry, but the "definition of standards for dust is a particularly complex issue...there are no agreed standards or guidelines for the nuisance impacts of mineral dusts in the UK." However The Air Quality Regulations 1997 do set a statutory objective for PM10 of 50μg/m3 or less, and the Environment Agency stipulates a maximum RCS level of 0.6μg/m3 around waste sites.

So, what are the benefits for a community newly saddled with this risk of airborne carcinogenic dust? DCC says "Mineral working at an individual site may take place over a number of decades and, while this timescale may seem a burden on local communities, it does offer the opportunity to develop strong working relationships between community and mineral operator [wow, thanks!] (as well as providing a source of local employment)." Blackhill Quarry currently employs nine. What about "the Aggregate Levy Sustainability Fund for projects in communities that are affected by aggregates extraction"? Scrapped in 2011.