From: "Secretary, ACS Division of Chemical Health and Safety" <secretary**At_Symbol_Here**DCHAS.ORG>
Subject: [DCHAS-L] Re; amorphous silica
Date: June 27, 2012 1:26:30 PM EDT
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <1D1C210A-2C88-4374-8988-9BB698E5FA80**At_Symbol_Here**DCHAS.ORG>

From: Rita Kay Calhoun
Subject: RE: [DCHAS-L] Toxic dust handling
Date: June 27, 2012 12:10:28 PM EDT

What about disposal of silica gel? If the column is stripped of sample, can it be sealed in a bag and disposed of in the trash? I'm talking about small amounts, certainly less than 2-300 grams.


From: Keith Rickabaugh
Subject: amorphous silica correction - - - RE: [DCHAS-L] Toxic dust handling
Date: June 27, 2012 12:29:44 PM EDT

I disagree with amorphous silica being cited as a "nuisance dust".

Independent of any toxicity issues, amorphous silica is a regulated substance by OSHA as per 29 CFR 1910.1000 (see table z-3). However, I believe that this is rarely (if ever) enforced. Even though there are reasonable arguments that this OSHA PEL reference value is outdated and may not be relevant - it is still the law.

The OSHA PEL is a calculated value that is based off of the percent of amorphous silica material in the particulate: 80 mg / % amorphous silica.

Many people are confused by this formula as they incorrectly think that the % silica in the formula is for crystalline silica.

If working with 100% amorphous silica, the PEL would 0.8 mg per cubic meter.

This is the one and only instance that I have noted that the OSHA PEL is actually lower than ACGIH TLV or NIOSH REL values.

See links below if interested in learning more:;94

Keith Rickabaugh

Technical Director, Materials & Analytical Services

RJ Lee Group

724.325.1776 Office
724.387.1841 Direct
724.309.6732 Mobile
724.733.1799 Fax

350 Hochberg Road | Monroeville, PA 15146

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