WHMIS Class D - Formulae for Equivalent LC50

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WHMIS - Class D - Formulae for Equivalent LC50 (Section 44)

The legal text of the regulations in section 44 follows below:

CPR: Section 44: Formulae for Equivalent LC50

For the purpose of establishing that a product, material or substance falls into Division 1 of Class D - Poisonous and Infectious Material, an LC50 that is obtained in an animal assay at an exposure duration of other than four hours may be converted to an LC50 equivalent to an exposure duration of four hours by using the following formulae:

(a) for a gas or vapour,

LC50 at Y hours × (Y hours)½/2 = LC50 at 4 hours; and

(b) for dust, mist or fume,

LC50 at Y hours × (Y hours)/4 = LC50 at 4 hours.

Note: Y = actual number of hours of exposure duration.

WHMIS MSDS Reference Manual - Section 44

Health Canada's WHMIS MSDS reference manual for section 44 is available at: WHMIS Requirements of the HPA and CPR, CPR Section 44. One of the important points they note is as follows:

"Four hour exposure periods are specified in paragraphs 46(c), (d) and (e) and in 49(c) and (d) of the Controlled Products Regulation s. Since LC50 determinations may be conducted over various periods of time measured in minutes to several hours, there is a need to be able to extrapolate such data for four hour exposure periods. These formulae assume a simple linear relationship between times of exposure and concentrations in the animal chamber for dust, mist and fume and a "square root" function for gas and vapour."

Nexreg Compliance WHMIS Canadian MSDS Authoring Services

Nexreg Compliance can author a WHMIS compliant Canadian MSDS for your product. For more information on Nexreg's WHMIS MSDS authoring services, please contact Nexreg Compliance or visit the following links:

Canadian Goverment Links

WHMIS MSDS NexregWiki Links

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