# Calcium carbonate — workplace exposure limit

For Calcium carbonate, niosh rel, as stated is TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp); cas no. is 471-34-1 (synthetic) 1317-65-3 (natural), verified against its source on 2026-09-08.

- **Substance:** Calcium carbonate _(verified: appears in its own passage below)_
- **CAS No.:** 471-34-1 (synthetic) 1317-65-3 (natural) _(verified: appears in its own passage below)_
- **NIOSH REL, as stated:** TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp) _(verified: appears in the quote below)_

## What the source says

> NIOSH REL TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)

## 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 - Calcium carbonate

### CAS No.

> CAS No. 471-34-1 (synthetic) 1317-65-3 (natural)

## Source

- https://www.cdc.gov/niosh/npg/npgd0090.html

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