Dust from Gravel Pit/Quarry Operations
Dust from pit and quarry activities that blows off site is often termed nuisance or fugitive dust. The standards of Ontario’s Aggregate Resources Act (ARA) , Section 3.0 Prescribed Conditions, Subsection 3.1 states “Dust will be mitigated on site.” The ARA definition of mitigate is: To alleviate, moderate or reduce the severity of impacts. Other definitions include: To rectify, repair or compensate for impacts, lessen or to try to lessen the seriousness or extent of. They are not required under the ARA to eliminate dust.
Dust Suppressants: Water spraying… requires frequent applications. CaCl2 and MgCl2, absorb moisture, but are toxic to plants and can potentially contaminate the aquifer. Oil derivatives pollute and lignin compounds, though safer, wash off.
Facts: Dust or airborne particulate matter (PM) varies in size. Total Suspended Particulate (TSP) refers to dust less than 100 microns in diameter. Large particles tend to settle quickly, smaller more harmful particles can be carried great distances. Dust is produced from blasting, crushing, screening and stacking operations as well as conveyor belts and loader and truck transport on site and trucks offsite. Dust is also produced during overburden removal and construction of berms and from wind blowing over stock piles and across barren pit floors. (Unlike excessive noise, dust has to be mitigated during construction). Dust increases corrosion and is harmful to vegetation.
Fine particulate matter, 10 microns or less in diameter (PM 10) can be inhaled and is considered toxic under the Canadian Environmental Protection Act (CEPA). Smaller respirable particulate matter, (PM 2.5) with a diameter of 2.5 microns or less, is even more dangerous, lodging deep within the lungs and tissue. There is no biological mechanism for clearing it from the body.
Recent studies show that fine particulates pose a greater danger to our health than better known kinds of air pollution, such as smog, sulphur dioxide and carbon monoxide. There is incontrovertible evidence that increased PM 10 is related to increases in cardiopulmonary disease, asthma, bronchitis, emphysema, pneumoconiosis and premature death in those with pre-existing conditions. The elderly and the young are most affected. Crystalline silica dust is common from processing sand and gravel and is a known carcinogen. Any dust report should include a specific analysis of crystalline silica content and dispersion.
Ontario General Air Pollution Regulation: This regulation, revoked and replaced on November 30, 2005 by O. Reg. 419/05, prescribes standards for permissible air emissions and the modelling requirements to determine compliance at the POI (point of impingement). An MOE Certificate of Approval is required in order to discharge into the natural environment. This usually requires a detailed report on all air emissions from a facility including an Emissions Summary Dispersion Modelling (ESDM) report (based on recent methods from the US EPA).
Canada Wide Standards (CWS) for PM were established in 2000. It is important to note however, that that there is no “safe” threshold of PM pollution. The “interim” standards are based on risk assessment “balanced” by the cost of implementation, with the input of “stakeholders”. A recent critical report ”The Air We Breathe”, by David Boyd (David Suzuki Foundation) recommends more stringent legally binding Canadian air quality standards (similar to the US, Australia and Europe).
Summary: Dust can kill you. Mitigation measures for pits and quarries are inadequate. Dust studies and instrument monitoring should be mandatory and include detailed analysis of specific mineral content (eg: silica, mica etc). MOE allowable PM standards do not go far enough, to ensure clean safe air.
See animation of inhaling air pollution particles.