# Methyl parathion — workplace exposure limit

For Methyl parathion, niosh rel (mg/m³) is TWA 0.2; cas no. is 298-00-0, verified against its source on 2026-09-08.

- **Substance:** Methyl parathion _(verified: appears in its own passage below)_
- **CAS No.:** 298-00-0 _(verified: appears in its own passage below)_
- **NIOSH REL (mg/m³):** TWA 0.2 _(verified: appears in the quote below)_
- **PEL (mg/m³):** 0.2 _(per dir.ca.gov, not stated by the source above)_

## What the source says

> NIOSH REL TWA 0.2 mg/m3 [skin]

## Where each value comes from

This source states these in separate places, so each value is shown with the passage that states it.

### Substance

> CDC - NIOSH Pocket Guide to Chemical Hazards - Methyl parathion

### CAS No.

> CAS No. 298-00-0

## What dir.ca.gov says

> 298000 | S | Methyl parathion; o,o-dimethyl o-(p-nitrophenyl) phosphorothioate | -- | 0.2

Source: https://www.dir.ca.gov/title8/5155.html

## Source

- https://www.cdc.gov/niosh/npg/npgd0427.html
- https://www.dir.ca.gov/title8/5155.html

Last verified: 2026-09-08. Review by: 2027-08-05.
Part of [US workplace chemical exposure limits: federal OSHA, Cal/OSHA and NIOSH, side by side](https://referencesource.org/workplace-exposure-limits/).