What is the tonnage threshold for TSCA on magnesium oxide (magnesia)?

CDR threshold: 25,000 lb manufactured or imported per site per year

CAS 1309-48-4 · TSCA · United States of America

Magnesium oxide (magnesia) under TSCA

MgO · 氧化镁

Status: Listed. Magnesium oxide is on the TSCA Inventory and currently listed as TSCA Active. **Federal OSHA Table Z-1 at 29 CFR 1910.1000 does NOT list a federally enforceable PEL for magnesium oxide fume; Cal/OSHA PEL is 15 mg/m3 and NIOSH REL is 10 mg/m3 (fume / total particulate, CAS 1309-48-4); verify against https://www.osha.gov/annotated-pels and https://www.cdc.gov/niosh/ before relying.** NOT on EPA RMP threshold list. NOT on DEA scheduling. NOT on California Proposition 65 (verify against OEHHA https://oehha.ca.gov/proposition-65/proposition-65-list before relying on negative listing). **US has historic AD/CVD scrutiny on Chinese-origin refractory-grade magnesia products (DBM and CCM), particularly Magnesia Carbon Bricks (MCB) AD/CVD orders A-570-954 / C-570-955 dating to 2010 (verify both case numbers and current cash-deposit rates against https://access.trade.gov/ before invoicing); the underlying MgO raw material has been subject to varying duty treatment over time.** Section 301 List 3 25% additional duty applies on Chinese-origin magnesia (HS 251990) (verify against current USTR Section 301 schedule before invoicing). **Food-grade GRAS** for magnesium oxide under 21 CFR 184.1431 (verify against https://www.ecfr.gov/ before relying); USP / NF monograph applies for pharma-grade. Major US domestic producers (verify each company-site pair against the producer's public website before relying): Premier Magnesia Hawesville Kentucky synthetic-magnesia operations, Martin Marietta Magnesia Specialties Manistee Michigan brine-extraction operations, Giles Chemical Waynesville North Carolina magnesia operations.

US magnesium oxide lane: **Federal OSHA Table Z-1 has NO PEL for MgO fume (Cal/OSHA PEL 15 mg/m3, NIOSH REL 10 mg/m3) + Magnesia Carbon Bricks AD/CVD orders A-570-954 / C-570-955 + Section 301 List 3 + GRAS / USP / NF for food-grade and pharma-grade**. NOT on Cal Prop 65. **MCB AD/CVD is the operative refractory-chain duty exposure; verify cash-deposit rates against access.trade.gov before invoicing.** Major US producers: Premier Magnesia (Kentucky), Martin Marietta (Michigan), Giles Chemical (North Carolina).

Listing and threshold

Substance	Magnesium oxide (magnesia) (CAS 1309-48-4), MgO
Regime	US Toxic Substances Control Act (TSCA), administered by EPA
Jurisdiction	United States of America
Status	Listed
Tonnage threshold	CDR threshold: 25,000 lb manufactured or imported per site per year

Classifications under this regime

OSHA HCS: NOT typically classified as hazardous beyond particulate dust / fume
Federal OSHA 29 CFR 1910.1000 Table Z-1: NO federally enforceable PEL listed for magnesium oxide fume (verify against https://www.osha.gov/annotated-pels)
Cal/OSHA PEL: 15 mg/m3 and NIOSH REL: 10 mg/m3 (fume / total particulate) (verify against https://www.osha.gov/annotated-pels and https://www.cdc.gov/niosh/)
NOT subject to TSCA Section 6 Risk Evaluation
NOT on EPA RMP threshold list
NOT on DEA List I or List II
NOT on California Proposition 65 list (verify against OEHHA before relying on negative listing)
DOT 49 CFR 172.101: NOT regulated
**Food-grade GRAS** 21 CFR 184.1431 (verify against https://www.ecfr.gov/)
**USP / NF monograph** applies for pharma-grade
IARC: Not classified

Restrictions and conditions of use

**US has historic AD/CVD scrutiny on Chinese-origin refractory-grade magnesia products via Magnesia Carbon Bricks (MCB) orders A-570-954 / C-570-955** (2010-origin, verify both case numbers and current cash-deposit rates against access.trade.gov before invoicing)
Section 301 List 3 25% additional duty applies on Chinese-origin magnesia (HS 251990)
Federal OSHA Table Z-1: NO PEL listed for magnesium oxide fume; Cal/OSHA PEL 15 mg/m3, NIOSH REL 10 mg/m3 (verify against osha.gov/annotated-pels)
Food-grade GRAS 21 CFR 184.1431 plus USP / NF monograph for pharma-grade

Importer obligations

TSCA self-certification regime. **Magnesia Carbon Bricks AD/CVD orders A-570-954 / C-570-955 are the operative duty exposure for the refractory-grade chain (verify against access.trade.gov before invoicing).** Major US producers (verify each producer-site pair before relying): Premier Magnesia Hawesville Kentucky, Martin Marietta Magnesia Specialties Manistee Michigan, Giles Chemical Waynesville North Carolina.

Required documents

TSCA Section 13 Import Certification on customs entry
OSHA SDS (with magnesium oxide fume / particulate dust handling notes)
CBP Form 7501 with HS 251990 + Section 301 List 3 25% duty
CDR filing every 4 years
AD/CVD entries for Magnesia Carbon Bricks scope (A-570-954 / C-570-955) where applicable
FDA / USP / NF certifications for food and pharma grades

Common compliance traps

The pitfalls that have bitten importers on this lane in the past. None of these is theoretical.

Federal OSHA Table Z-1: NO PEL listed for magnesium oxide fume; Cal/OSHA PEL 15 mg/m3, NIOSH REL 10 mg/m3 (verify against osha.gov/annotated-pels)
**Magnesia Carbon Bricks AD/CVD orders A-570-954 / C-570-955** (verify against access.trade.gov before invoicing)
Section 301 List 3 25% additional duty applies
Food-grade GRAS 21 CFR 184.1431 plus USP / NF monograph for pharma-grade
Major US producers: Premier Magnesia Hawesville KY, Martin Marietta Manistee MI, Giles Chemical Waynesville NC (verify each producer-site pair)

Where to read next

For substance-level identifiers (formula, molecular weight, SMILES, InChIKey), GHS hazard profile, IMDG transport class, and full sourcing reference for magnesium oxide (magnesia), see the CAS 1309-48-4 sourcing reference.

For grade-by-grade buying notes, freight maths, supplier-tier pricing, and a worked landed-cost example, the magnesium oxide (magnesia) cornerstone hub covers the full sourcing chain.

For the structure and history of TSCA, see the TSCA glossary entry.

Need cross-jurisdiction compliance support on this substance? Run it through the REACH / TSCA / IECSC / AICIS / K-REACH checker, or send us the substance and the destination and we will quote FOB China and CIF / DDP landed including the regulatory work on the destination side.

Cross-jurisdiction profile and sourcing references

Referenced in

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