Goals of Air Monitoring around sand mines
The community-defined goals of monitoring the air around sand mining operations are:
- Identify the health impacts of mining-related air pollution
- Document the impacts of sand mining operations so they can be used as evidence in judgements against mines, transfer facilities, and transporters.
- Identify when respirable silica levels are high so mitigation measures can be taken.
Meeting these goals requires affordable tools that connect particles back to the source, document PM with techniques admissible in regulatory judgements, and report PM concentrations in real time. No single tool has all of these capabilities, but a combination of several tools and advocacy can approach the monitoring goals.
Challenges to Monitoring
Connecting particles to the source
Atmospheric particles can be long lived and travel long distances. Detecting a high levels of PM or a specific pollutant does not necessarily tie the measurement back to its source, even if the nearby industry is associated with that type of pollutant. Three strategies are used to correlate air pollution with its source:
- baseline monitoring before a facility begins operations to establish background levels of PM.
- distributing monitors around a facility, or at least up and down wind in order to demonstrate an increase down wind.
- identifying (‘speciation’) the types of PM collected and demonstrating airborne concentrations high enough that they must have a local source.
Baseline monitoring requires affordable equipment that can be kept running over a long period, usually years. Distributing monitors around a facility requires the monitors to be affordable enough for multiples, and often means placing monitors in hard-to-service areas without access to electricity. Identifying particles and their airborne concentration often requires expensive lab testing and even more expensive instruments.
In the case of sand mining, silica is present in the soil and shows up as a sizable component of background dust. Identifying (’speciating’) silica in PM samples isn’t enough to tie it back to a facility. Either baseline monitoring or distributed monitors could provide that assurance.
Speciating silica may be still be helpful as local levels of silica PM could pose a health threat without meeting regulatory action levels for all PM2.5 or PM10.
Documenting PM to regulatory standards
Situating monitoring in relationship to regulatory standards is important to making monitoring data comparable to other monitoring programs and seeking regulatory outcomes. The US EPA is working to establish tiers of data quality for supplementary monitoring and personal exposure, with a lower barrier to acceptance than regulatory monitoring (/wiki/PM-monitoring-regulation).
Current national air quality standards do not include silica directly, although they assume a certain level of respirable silica exposure. The ‘action level’ for PM10 is an annual mean of assuming 10%, or 5μg/m3 silica, while non-occupatial exposure of ~15μg/m3 of PM10 is correlated with significant increases in silicosis. Dangerous levels of non-occupational exposure to silica are therefore possible at or below regulatory action levels for PM, suggesting that identifying, or speciating, particles is an important component of understanding the health effects of sand mining.
Citation: L. J. Bhagia, Non-occupational exposure to silica dust, Indian J Occup Environ Med. 2012 Sep-Dec; 16(3): 95–100.
Documenting PM in real-time
Real-time monitoring of PM requires the use of a real-time optical monitoring system. Affordable optical monitors do not usually collect particles for identification (‘speciation’), and more expensive ($1500+) monitors’ filter-collected PM can only be speciated in expensive lab processes(LINK to optical pm section on PDR-1500/Dusttrak). Low-cost optical monitors have been used to [force regulatory-grade monitoring and raise awareness] (case study on CCC Dylos).
Real-time monitors are uniquely capable of capturing spikes in activity and are useful for correlating different activities with releases of particles, as well as mitigating the health effects of particle pollution.
TBD finishing filter systems & optical systems page first