I've been concerned about the sand we used in our first year.
it seems with hopper or by shovel method, it creates a lot of airborne dust.
i've read up on silicon carbide and based on this info and some other quick searches...http://nj.gov/health/eoh/rtkweb/documents/fs/1658.pdf
i did not want the kids to be exposed to it.
we purchased 2 boxes of "safe sand" from lakeshorehttp://www.lakeshorelearning.com/produc ... p4CQkyrCU-
still having the kids use a mask while loading the bucket.
Just some perspective:
Being aware of inhalation hazards posed by dust (when... sand-like material falls into the load bucket), and minimizing them is very appropriate. But it is important to understand that both silicon carbide and sand (silicon dioxide, SiO2
, "silica, quartz") represent similar hazards/health risks, adverse exposure risks, and both are regulated as hazardous materials in the workplace. SiO2
is actually classified as a higher health risk because it is classified as a known carcinogen (vs silicon carbide classified as a possible carcinogen).
Here's the NJ Government warning sheet on it (to compare with the silicon carbide one); similar allowed/recommended workplace exposures, http://nj.gov/health/eoh/rtkweb/documents/fs/1660.pdf
In doing risk assessment, its important to understand you need to look at concentration of exposure and duration of exposure.. Exposure/risk is based on 'dose', the concentration, times the exposure time, The OSHA permissible exposure limits (PELs) are set for allowable concentrations in a worker's breathing zone for 8 hrs of continuous exposure; the NIOSH and ACGIH 'recommended' exposure limits are set for 10 hrs of continuous exposure. At a tower/bridge/boom loading, the 'bucket holder' student is not going to be in a position to be respiring dust from 'sand' loading for much more than a minute. So at whatever air concentration, they're getting 1/480th of what a worker would get over an 8 hr shift.
Having done some industrial hygiene air monitoring for airborne dust, and sand blasting with silicon carbide, and having watched many tower, bridge, boom loadings at S.O. events over 10+ years, my... observations are, if you're using really "dirty" sand (poorly sorted, lots of fines among the larger grains), you might be approaching concentrations that would be of concern for an 8hr exposure within a foot , maybe a foot and a half of the bucket. With well sorted/clean/washed sand, very minimal dust, well below levels of concern. With silicon carbide, particularly the larger particle size dholdgreve recommended, virtually no dust, well below levels of concern.
Having said this, I need to say, I am not providing this information/discussion as a formal expert opinion, and readers should not rely on it to assess potential exposure levels and associated health risks. If any coach, student, parent , event supervisor (or person affiliated with Science Olympiad), they should have potential exposures evaluated by a properly qualified expert (e.g, Certified Industrial Hygienist - CIH)
Hopes this helps.