A number of commercially available epoxy coatings designed for underwater application contain a very dangerous chemical in their curing agents. That chemical is 4,4' Methylenedianiline commonly called MDA. Users of epoxy coatings should check their MSDS sheets for mention of this chemical.

Medical concerns over MDA regards its liver toxicity and carcinogenicity. OSHA exposure limits are set at only 8 parts per billion.

Coating concerns with MDA are that it tends to crystallize sold and is very brittle. Additionally, it requires not just hazmat shipping but also special ‘Keep away from foodstuffs' labels.

Below is the actual text from OSHA regards MDA:

The Department of Labor (OSHA) has published 29 CFR Parts 1910 and 1926, Occupational Exposure to 4,4' Methylenedianiline (MDA) which classifies MDA as a dangerous substance and a carcinogen. The basis for "promulgating new standards regulating exposure to MDA...is a determination by the Assistant Secretary, based on animal and human data, that exposure to MDA at the current occupational exposure levels causes adverse effects on employee health including an increased risk of cancer and that limiting occupational exposure to MDA to an eight-hour time-weighted average (TWA) of 10 parts per billion (ppb), establishing a short-term exposure limit (STEL) of 100 ppb". In addition to establishing permissible exposure limits (PELs) for MDA, this regulation includes requirements such as medical surveillance, exposure monitoring, hygiene facilities, engineering controls and work practices, proper respirator use, and record keeping.

"The standards apply to all industries covered by the OSH Act including general industry, construction, and maritime. These final rules shall become effective on September 9, 1992."