In April 2024, the EPA issued a final rule regulating methylene chloride aka dichloromethane under the Toxic Substances Control Act (TSCA). The rule prohibits consumer use and significantly limits commercial use. However, laboratory use is exempted under the prohibitions. The EPA provides a fact sheet summarizing requirements under the rule.
To continue using methylene chloride under the laboratory use exemption, WSU must develop a workplace chemical protection program which includes exposure monitoring. Initial exposure monitoring must be completed by May 5, 2025. If you use methylene chloride in your laboratory, contact EH&S at 509-335-0948 or tom.ebeling@wsu.edu for assistance. The following table summarizes exposure monitoring requirements:
Periodic Monitoring Requirements Based on Initial Exposure Monitoring Results
| Air Concentration Condition | Periodic Monitoring Requirement |
| If the initial exposure monitoring concentration is below the Existing Chemical Exposure Limit (ECEL) action level of 1 ppm and at or below the Short Term Action Level (STEL) of 16 ppm | ECEL and STEL periodic exposure monitoring at least once every 5 years |
| If the initial exposure monitoring concentration is below the ECEL action level and above the STEL | ECEL periodic exposure monitoring at least once every 5 years and STEL periodic exposure monitoring every 3 months |
| If the initial exposure monitoring concentration is at or above the ECEL action level and at or below the ECEL; and below the STEL | ECEL periodic exposure monitoring every 6 months |
| If the initial exposure monitoring concentration is at or above the ECEL action level and at or below the ECEL; and above the STEL | ECEL periodic exposure monitoring every 6 months and STEL periodic exposure monitoring every 3 months |
| If the initial exposure monitoring concentration is above the ECEL action level and below, at or above the STEL | ECEL periodic exposure monitoring every 3 months and STEL periodic exposure monitoring every 3 months |
| If 2 consecutive monitoring events have taken place at least 7 days apart that indicate exposure has decreased from above the ECEL to at or below the ECEL, but at or above the ECEL action level | Transition from ECEL periodic exposure monitoring every 3 months to every 6 months |
| If 2 consecutive monitoring events have taken place at least 7 days apart that indicate exposure has decreased to below the ECEL action level and below the STEL | Transition from ECEL periodic exposure monitoring every 6 months to once every 5 years |
| If based on exposure monitoring results the owner or operator is required to monitor exposure in 3 or 6 month intervals, but does not use methylene chloride | The owner or operator may forgo the periodic monitoring, but must document the cessation of use, and resume monitoring if/when using methylene chloride |
Note: The ECEL will require that methylene chloride use is limited to fume hoods, incorporates other hazardous exhaust, or closed systems. Use outside of a hood will likely require respiratory protection, which under the rule requires the provision of supplied air respirators (SAR) or self-contained breathing apparatus (SCBA).