General Industry (29 CFR 1910)

Methylenedianiline (MDA)

Verified vs OSHA sources · 2026-10-05

29 CFR 1910.1050

29 CFR 1910.1050 protects general-industry workers from 4,4'-methylenedianiline (MDA), a curing agent in epoxy resins and a carcinogen and liver toxin that is readily absorbed through the skin. It caps exposure at 10 ppb as an 8-hour TWA with a 100 ppb 15-minute STEL and a 5 ppb action level, requiring monitoring, controls, skin protection, and medical surveillance.

29 CFR 1910.1050 at a glance

PEL: 10 ppb as an 8-hour TWA (29 CFR 1910.1050(c))
STEL: 100 ppb over any 15-minute period (1910.1050(c))
Action level: 5 ppb (8-hr TWA): triggers monitoring and medical surveillance
Key route: Skin absorption (dermal) as well as inhalation
Max penalty (2026): $16,550 per serious violation; $165,514 per willful
The #1 confusion: Much of the MDA dose is dermal: air monitoring alone does not capture skin uptake

What 29 CFR 1910.1050 requires (plain English)

29 CFR 1910.1050 protects general-industry workers from 4,4'-methylenedianiline (MDA), an aromatic amine used mainly as a curing agent and hardener for epoxy resins and as an intermediate in making polyurethanes and other polymers. It is a carcinogen and a potent liver toxin, and it is readily absorbed through the skin.

The standard sets a permissible exposure limit of 10 ppb as an 8-hour time-weighted average and a short-term exposure limit of 100 ppb over any 15 minutes, with an action level of 5 ppb that triggers monitoring and medical surveillance. Because MDA is absorbed dermally, the standard emphasizes protective clothing and gloves, hygiene, and prevention of skin contact alongside airborne controls; engineering controls, regulated areas, respirators, and training round out the requirements.

1910.1050 is a Subpart Z substance-specific health standard (a parallel construction standard, 1926.60, covers construction work). Its distinctive feature is the emphasis on dermal protection, because for MDA the skin route can dominate the total dose.

The regulatory text

“The employer shall assure that no employee is exposed to an airborne concentration of MDA in excess of ten parts per billion (10 ppb) as an 8-hour time-weighted average or a STEL of 100 ppb.”

29 CFR 1910.1050(c)

Key facts about 29 CFR 1910.1050

The MDA PEL is 10 ppb as an 8-hour TWA (1910.1050(c)).
A short-term exposure limit caps exposure at 100 ppb over any 15 minutes (1910.1050(c)).
The action level is 5 ppb (8-hr TWA) and triggers monitoring and medical surveillance.
MDA is a carcinogen and a potent liver toxin.
It is readily absorbed through the skin, so dermal protection is essential.
Its main use is as an epoxy curing agent and hardener and a polymer intermediate.
A parallel construction standard, 1926.60, covers construction work.

Scope: who 29 CFR 1910.1050 applies to

Regulatory framework: General Industry (29 CFR 1910)
Citation reference: 29 CFR 1910.1050
Enforcement status: In force and enforced
Jurisdiction: Federal OSHA (29 State-Plan jurisdictions may be stricter)

State-Plan states (e.g. California, Washington, Michigan) operate OSHA-approved programs that must be at least as effective as federal OSHA and frequently impose higher penalties or additional requirements. Confirm the rule as adopted in your state.

Key requirements of 29 CFR 1910.1050

#	Employer obligation
1	Limit exposure to 10 ppb PEL
2	STEL of 100 ppb (15-minute)
3	Monitor exposure above action level (5 ppb)
4	Provide medical surveillance
5	Establish regulated areas
6	Prevent skin contact with MDA

Summarized from the text of 29 CFR 1910.1050. Always read the full regulation for the binding language.

Common MDA violations

Deficiencies OSHA cites under 29 CFR 1910.1050 include the ones below, in no particular order. Distinct deficiencies can be cited as separate items, and each serious item carries up to $16,550 (2026). Broader per-instance stacking exists but is a discretionary, case-by-case OSHA enforcement policy, not an automatic multiplier.

No exposure monitoring where MDA-containing products are used (1910.1050(e)).
No protective clothing or gloves to prevent skin contact (1910.1050(h) and (i)).
No medical surveillance for workers at or above the action level (1910.1050(m)).
Exposures above the PEL or STEL without adequate controls (1910.1050(g)).
No regulated area where exposure exceeds the PEL or STEL (1910.1050(f)).

For MDA, the skin route can matter more than the air: air monitoring alone is not enough

A frequent mistake is to judge MDA exposure by air-monitoring results alone. MDA is readily absorbed through the skin, and when workers handle epoxy curing agents and hardeners, dermal uptake (from splashes, contaminated gloves, and surface contact) can deliver more of the dose than inhalation. That is why 1910.1050 requires protective clothing and gloves, hygiene facilities, and measures to prevent skin and eye contact, not just airborne controls to the 10 ppb PEL. A workplace that meets the air limit but lets workers get MDA on their skin has not controlled the real exposure.

What OSHA inspectors look for

A compliance officer checks exposure monitoring where MDA-containing epoxies and curing agents are used, verifies engineering controls and skin protection (MDA is absorbed dermally), and confirms liver-focused medical surveillance above the action level. Skin contact with epoxy curing agents without gloves is a common finding.

Example: how a violation is cited

Workers handling an MDA-based epoxy curing agent get it on bare skin while mixing, with no gloves or surveillance: MDA is absorbed through the skin and damages the liver. OSHA cites 1910.1050 for the exposure and missing controls, with penalties from $16,550.

Illustrative example, not a specific OSHA case.

MDA compliance checklist

Use this to evaluate your compliance with 29 CFR 1910.1050. Each item is a key requirement OSHA may verify during an inspection.

Identify MDA-containing epoxies, hardeners, and processes and monitor exposures.
Provide impervious gloves and protective clothing and prevent skin and eye contact.
Reduce airborne exposure to the 10 ppb PEL and 100 ppb STEL with engineering controls.
Provide liver-focused medical surveillance for workers at or above the 5 ppb action level.
Establish regulated areas and hygiene facilities where exposure exceeds the limits.
Train workers on the dermal-absorption and liver and cancer hazards.

2026 penalties for 29 CFR 1910.1050

Maximums set by 29 CFR 1903.15(d). 2026 amounts unchanged from 2025 (no CPI adjustment; OMB M-26-11). Not an increase. The 2025 OSHA penalty levels remain in effect for 2026; OSHA made no inflation adjustment for 2026. 29 CFR 1903.15 identifies January 15, 2025 as the effective reference for these amounts, while OSHA's public penalties page currently references penalties assessed after Jan. 15, 2026.

Violation type	Minimum	Maximum	When it applies
Serious	$1,085	$16,550	Substantial probability of death or serious physical harm.
Other-Than-Serious	$0	$16,550	Relates to safety/health but unlikely to cause death or serious harm.
Willful	$11,823	$165,514	Intentional, knowing, or voluntary disregard of the requirement.
Repeated	$4,256	$165,514	A substantially similar violation cited within the last 5 years.
Failure to Abate	None	$16,550/day	up to $16,550 per day; total capped at 30x the daily amount (FOM Ch.6)

MDA citations follow health inspections of epoxy, composite, and coatings operations. Serious violations reach $16,550 and willful or repeat violations $165,514; skin contact without gloves and no surveillance are the usual findings.

Maximums and the willful minimum are set by 29 CFR 1903.15(d); the serious and repeated minimums are OSHA policy floors from its annual penalty adjustment memo. OSHA applies gravity-based and size, good-faith and history reductions (FOM CPL 02-00-164 Ch.6). Estimates only, not legal advice.

The business case for MDA compliance

MDA is a carcinogen and a potent liver toxin, and, unusually, a large share of the dose can come through the skin, not just inhalation, when workers handle epoxy curing agents. Controlling airborne exposure to the 10 ppb PEL and preventing skin contact is what protects epoxy, composite, and coatings workers from liver damage and cancer.

Free compliance tools for 29 CFR 1910.1050

SDS Gap Analyzer PPE Selector Respiratory Protection Program Builder

MDA penalties by state

Penalties and enforcement vary by state. State-Plan states may impose higher penalties and additional requirements beyond federal 29 CFR 1910.1050.

Alabama Arkansas Colorado Connecticut Delaware District of Columbia

View all 50 states + DC →

Frequently asked questions about 29 CFR 1910.1050

What is the OSHA MDA PEL?

Under 1910.1050(c), the permissible exposure limit for 4,4'-methylenedianiline (MDA) is 10 ppb as an 8-hour time-weighted average, with a short-term exposure limit of 100 ppb over any 15-minute period. An action level of 5 ppb (8-hour TWA) triggers exposure monitoring and medical surveillance.

Why does MDA require skin protection?

Because MDA is readily absorbed through the skin, and for many tasks the dermal route delivers a large share of the total dose. Workers handling MDA-based epoxy curing agents can absorb it from splashes and contaminated gloves even when air concentrations are low. 1910.1050 therefore requires protective clothing, impervious gloves, hygiene facilities, and measures to prevent skin and eye contact, in addition to airborne controls.

What health effects does MDA cause?

MDA is a carcinogen and a potent liver toxin. Acute overexposure can cause toxic hepatitis (liver injury), and long-term exposure carries cancer risk. That is why medical surveillance under 1910.1050 focuses on liver function for workers exposed at or above the action level, so early effects can be detected and exposure reduced.

Is there a separate MDA standard for construction?

Yes. 29 CFR 1910.1050 covers general industry, and 29 CFR 1926.60 covers construction work with MDA, for example, applying MDA-containing coatings, grouts, and epoxy systems on construction sites. The two standards are closely parallel, both setting a 10 ppb PEL and 100 ppb STEL with monitoring, dermal protection, and medical surveillance.

Regulatory history of 29 CFR 1910.1050

OSHA issued the MDA standards for general industry (1910.1050) and construction (1926.60) in 1992 (57 FR 35630) after evidence of liver toxicity and cancer, setting the 10 ppb PEL and 100 ppb STEL and, distinctively, strong dermal-protection requirements because MDA is absorbed through the skin.

Related glossary terms

Key terms that appear in 29 CFR 1910.1050, each with a full plain-English explainer.

Permissible Exposure Limit (PEL)Action Level Medical Surveillance Engineering Controls Personal Protective Equipment (PPE)Safety Data Sheet (SDS)

Related guides & articles

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29 CFR 1910.1000

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29 CFR 1910.1001

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29 CFR 1910.1003

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29 CFR 1910.1018

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Primary sources

OSHA figures on this page are imported from HazComFast's verified regulatory module (verified 2026-10-05 against eCFR, OSHA.gov, and the Federal Register).

This page is an educational summary, not legal advice. OSHA standards and penalty amounts change; confirm requirements against the current regulation and your applicable State-Plan before acting.

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OSHA does not give advance notice of inspections (29 CFR 1903.6). Get the binder in order before the opening conference, not during it.

Serious Violation

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