# 1,3,5-Trimethylbenzene — workplace exposure limit

For 1,3,5-Trimethylbenzene, niosh rel (ppm) is TWA 25; niosh rel (mg/m³) is 125; cas no. is 108-67-8, verified against its source on 2026-09-08.

- **Substance:** 1,3,5-Trimethylbenzene _(verified: appears in its own passage below)_
- **CAS No.:** 108-67-8 _(verified: appears in its own passage below)_
- **NIOSH REL (ppm):** TWA 25 _(verified: appears in the quote below)_
- **NIOSH REL (mg/m³):** 125 _(verified: appears in the quote below)_

## What the source says

> NIOSH REL TWA 25 ppm (125 mg/m3)

## 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 - 1,3,5-Trimethylbenzene

### CAS No.

> CAS No. 108-67-8

## What dir.ca.gov says

> 108678 | | Mesitylene; see 1,3,5-Trimethylbenzene

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

## Source

- https://www.cdc.gov/niosh/npg/npgd0639.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/).