F o r -  le by th e S u p e rin te n d e n t of D o c u m e n ts, U .S . G o vem m en t P rin tin g O ffic e , W ash in g to n , D .C . 20402 HEW Publication No. (NIOSH) 76-138 PREFACE The Occupational Safety and Health Act of 1970 emphasizes the need for standards to protect the health and safety of workers exposed to an ever-increasing number of potential hazards at their workplace. The National Institute for Occupational Safety and Health has projected a formal system of research, with priorities determined on the basis of specified indices, to provide relevant data from which valid criteria for effective standards can be derived. Recommended standards for occupational exposure, which are the result of this work, are based on the health effects of exposure. The Secretary of Labor will weigh these recommen dations along with other considerations such as feasibility and means of implementation in developing regulatory standards. It is intended to present successive reports as research and epide miologic studies are completed and as sampling and analytical methods are developed. Criteria and standards will be reviewed periodically to ensure continuing protection of the worker. I am pleased to acknowledge the contributions to this report on methylene chloride by members of my staff and the valuable constructive comments by the Review Consultants on methylene chloride, by the ad hoc committees of the American Industrial Hygiene Association and the American Academy of Occupational Medicine, by Robert B. O'Connor, M.D., NIOSH consultant in occupational medicine, and by William M. Pierce on respiratory protection and work practices. The NIOSH recommendations for standards are not necessarily a consensus of all the consultants and pro fessional societies that reviewed this criteria document on methylene chloride. Lists of the NIOSH Review Committee members and of the Review Consultants appear on the following pages.# CRITERIA DOCUMENT:

# RECOMMENDATIONS FOR AN OCCUPATIONAL EXPOSURE STANDARD FOR METHYLENE CHLORIDE
"Occupational exposure to methylene chloride" is defined as exposure above one-half the daily time-weighted average (TWA) exposure limit, except when there is also exposure to carbon monoxide (CO) at more than 9 ppm.
Because the toxicities of CO and methylene chloride are additive, the appropriate environmental limit and action level of methylene chloride must be reduced in the presence of CO. When CO levels are more than 9 ppm "occupational exposure to methylene chloride" shall be determined from the (3) Only appropriate respirators as described in Table 1-  Less than or equal 1) Any supplied air respirator, to 3,750 ppm (50X) with full facepiece, helmet or hood. 2) Any self-contained breathing apparatus with full facepiece.
3,750 ppm or more 1) Self-contained breathing apparatus, pressure demand mode (positive pressure), in full facepiece.
Combination supplied air respira tor, pressure demand mode, with auxiliary self-contained air supply.
Evacuation or escape 1) Any escape-type, self-contained (no concentration breathing apparatus. limit)
2) Any escape--type gas mask providing protection against methylene chloride (C)
The employer shall provide respirators in accordance with  (E) Respirators specified in Table 1-  However, records which form the basis for concluding that the exposures are below one-half the limit shall be maintained and exposure surveys shall be made when any process change indicates the need for reevaluation or at the discretion of the compliance officer.

# (b)
Where exposure concentrations have not been determined, they shall be determined within 6 months of the promulgation of a standard incorporating these recommendations.
(c) Where it has been determined that environmental concentrations result in TWA workday exposures above one-half the limit, employers shall maintain records of environmental exposures to methylene chloride based upon the following sampling and recording schedules:
(1) Samples shall be collected at least every 6 months in accordance with Appendix I for the evaluation of the work environment with respect to the recommended standard.
(2) Environmental samples shall be taken when a new process is installed or when process changes are made which may cause an increase in environmental concentrations. Increased production, relocation of existing operations, and increased overtime also requires resampling.
(3) In all monitoring, samples shall be collected which are representative of breathing-zone exposures characteristic of each job or specific operation in each work area.        The method of analysis was not given.
The hands and arms of the chemist were also exposed to liquid methylene chloride when the salt was removed from the distillation apparatus.
After           A disadvantage of the method is the indirect system of measurement requiring collection and desorption prior to analysis.
(  The Czechoslovak Committee of MAC listed standards for Hungary (6 ppm), Great Britain (500 ppm) and GDR (141 ppm).
 The Czechoslovak Committee considered that contamination of methylene chloride with methyl chloride was the reason for the low USSR standard.
The 1969 ANSI Z-37 standard  was adopted as the federal standard, 29 CFR 1910.1000, Table G2. This standard is a TWA of 500 ppm for an 8 hour/day, a ceiling concentration of 1,000 ppm, and a maximum peak of 2,000 ppm for no more than 5 minutes in any 2 h o u r s . Human male subjects (nonsmokers) exposed experimentally to methylene chloride for 7.5 hours daily on 5 consecutive days attained average peak COHb percentages of 2.9% at 50 ppm methylene chloride, 5.7% at 100 ppm methylene chloride, and 9.6% at 250 ppm methylene chloride.

# Basis for Recommended Environmental
In each case, the peaks were attained on the 5th day of exposure.
The date and time of sample collection.
(2) Sampling duration.
(3) Total sample volume.
(4) Location of sampling.

# MATERIAL SAFETY DATA SHEET

# PRODUCT IDENTIFICATION

# U N U S U A L F IR E A N D E X P L O S IO N H A Z A R D V HEALTH HAZARD INFORMATION H E A L T H H A Z A R O D A T A R O U T E S O F E X P O SU R E IN H A L A T IO N S K IN C O N T A C T S K IN A B S O R P T IO N E Y E C O N T A C T IN G E S T IO N E F F E C T S OF O V E R E X P O S U R E A C U T E O V E R E X P O S U R E C H R O N IC O V E R E X P O S U R E E M E R G E N C Y A N D F IR ST