Skip directly to site content Skip directly to search


Español  Other Languages


Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People
 Search
		×
			NIOSH
			NIOSH
				All CDC
				Submit
			For a full list of topics:A-Z Index
			Advanced Search
		Advanced Search


The National Institute for Occupational Safety and Health (NIOSH)








CALCIUM HYDROXIDE										Related Pages
										*OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.*
**CAS:** 1305-62-0; **Chemical Formula:** CaOH2
OSHA formerly had no individual limit for calcium hydroxide consequently the nuisance dust limit applied, the ACGIH has a TLV-TWA of 5 mg/m3. In the proposal, the PEL was 5 mg/m3 as an 8-hour TWA, and NIOSH (Ex. 8-47, Table N1) concurred with this limit. The final rule promulgates an 8-hour TWA PEL of 5 mg/m3 for calcium hydroxide. Calcium hydroxide is a soft, white, odorless, crystalline powder with an alkaline, bitter taste.
Calcium hydroxide is a moderate to severe caustic irritant when it comes in contact with the skin, eyes, or mucous membranes of the upper respiratory tract (ACGIH 1986/Ex. 1-3, p. 92; Sax and Lewis 1989, p. 682). The oral LD(50) in rats is reported to be 7.34 g/kg (Smyth, Carpenter, Weil et al. 1969/Ex. 1-442). Industrial experience with this substance has not shown a high incidence of adverse health effects, although Sax (Dangerous Properties of Industrial Materials, 6th ed., 1984) reports that it is known to cause dermatitis (p. 621). Calcium hydroxide is also mutagenic (Dangerous Properties of Industrial Materials, 7th ed., Sax and Lewis 1989, p. 682). Calcium hydroxide has less alkalinity than the hydroxides of the alkali series, and the ACGIH has suggested that limits for exposures to calcium hydroxide should be based on its total alkalinity.
OSHA received only one comment other than NIOSH’s on calcium hydroxide. The National Lime Association (NLA) (Ex. 3-890) raised several issues related to this substance. First, the NLA argues that the health evidence for calcium hydroxide does not support a PEL of 5 mg/m3 for this substance. According to the NLA, the oral toxicity study described by OSHA in the proposal has no relevance to airborne lime exposures (Ex. 3-890, p. 13). In addition, the NLA believes that calcium hydroxide should be regulated as a nuisance dust, with a PEL of 10 mg/m3. OSHA does not agree that calcium hydroxide is a biologically inert substance. The Agency agrees with Sax (1984), who reports that, “in the form of dust, it [calcium hydroxide] is considered to be an important industrial hazard.” OSHA finds that a PEL of 5 mg/m3, half that of the proposed inert particulate limit, is appropriate for this well-known eye, skin, and upper respiratory tract irritant.
The NLA’s second point is that the monitoring methods available for measuring workplace exposures to lime are inadequate to distinguish between “different compounds of calcium” because they are “element- not compound-specific” (Ex. 3-890). OSHA’s decision in the final rule to establish 5-mg/m3 limits for both calcium oxide and calcium hydroxide (see the discussion below for calcium oxide) should eliminate this problem for affected employers.
In the final rule, OSHA is establishing an 8-hour TWA limit for calcium hydroxide of 5 mg/m3 to protect against the significant risk of skin, eye, and mucous membrane irritation, which are material impairments of health that are caused by exposure to this substance at levels above the new PEL. The Agency concludes that this limit will reduce these risks substantially.
							
					
							Last Reviewed:  September 28, 2011						Source: 	National Institute for Occupational Safety and Health
					Facebook
        Twitter
        LinkedIn
        Syndicate NIOSH
1988 OSHA PEL Project Documentation
Index of Chemical Names
Index of CAS Numbers Follow NIOSH Facebook
Pinterest
Twitter
YouTube
 NIOSH Homepage NIOSH A-Z
Workplace Safety & Health Topics
Publications and Products
Programs
Contact NIOSH


About CDC
					Contact Us
					800-232-4636
 Facebook Twitter Instagram LinkedIn Youtube Pinterest Snapchat
 CONTACT CDC
				Contact Us
							Call 800-232-4636
							Email Us
			ABOUT CDC
				About CDC
							Jobs
							Funding
			POLICIES
				Accessibility
							External Links
							Privacy
							Policies
							No Fear Act
							FOIA
							OIG
							Nondiscrimination
							Vulnerability Disclosure Policy
			CONNECT WITH US
				Facebook
								Twitter
								Instagram
								LinkedIn
							Youtube
								Pinterest
								Snapchat
								Email
			LANGUAGES
				Español
							繁體中文
							Tiếng Việt
							한국어
							Tagalog
							Русский
							العربية
							Kreyòl Ayisyen
							Français
							Polski
							Português
							Italiano
							Deutsch
							日本語
							فارسی
							English


U.S. Department of Health & Human Services
			Accessibility
			External Links
			Privacy
			Policies
			No Fear Act
			FOIA
			Nondiscrimination
			OIG
			Vulnerability Disclosure Policy
			USA.gov


Exit Notification / Disclaimer Policy Close
 Links with this icon  indicate that you are leaving the CDC website. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
				Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
				You will be subject to the destination website's privacy policy when you follow the link.
				CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. Website Disclaimers
 Cancel Continue