Shop Tips » Working With Epoxy and Fiberglass
Safe Boatbuilding (Part 2) by Dave Carnell
. . . Back to part 1
These are the general rules for keeping out of trouble with hazardous chemicals. Let's take a look some specific materials, their hazards, and procedures for using them safely;
Most have no vapor problems. [This means there is no odor from our MAS epoxies, and MAS epoxies present no explosion hazard.]
The hazard is sensitization by the hardeners from excessive skin contact. If you work should with epoxy resins you should have no problems. If you become sensitized (rashes, dermatitis, or allergy reactions) it is unlikely to reverse. You may not be able to go back to using epoxies.
Sensitization susceptibility varies among people. In general, the less hardener required in a recipe, the more likely it is to cause sensitization; that is, 10/1 mixes are most potent; 1/1, least.
I strongly prefer epoxy resins to styrene-laced polyester resins because the overall working hazards are fewer and are much more easily manageable.
In addition, they are superior engineering materials with respect to adhesion, reliability of curing, and compatibility with other materials, such as wood and foams.
This is the most commonly encountered chemical hazard in boat building and perhaps the most hazardous. Over 300 varieties of wood have been reported to cause dermatitis. Heartwoods are worse than sap woods (probably because of the natural poisons they contain, which also make them more resistant to decay).
The exposure limit is 5mg/m3 (cubic meter) for all woods except western red cedar, which is 2.5mg/m3 because one in 20 people is allergic to red cedar dust. These are exposures for 8hr. working days. The short time exposure limit is only 10mg/m3.
OSHA's physiological reason for the wood dust limit is to avoid respiratory effects.
OSHA noted that the International Agency for Research on Cancer classifies furniture manufacturing as a source of "confirmed human carcinogen" and carpentry as a source of "suspected human carcinogen" in people -- not mice, rats, or guinea pigs. Cancer is caused by long term exposure to an agent. With wood dust, as with nearly all of the chemicals regulated, OSHA concluded that avoiding exposures that can cause immediate acute effects would also protect against cancer over the long term.
How much dust is that? In a 20' by 20' by 10' high shop, a half-teaspoon of fine wood dust distributed uniformly in the air would be a concentration of 5mg/m3. That is not much and is the reason you should always wear dust protection when sanding.
Lauan mahogany dust is a bad actor, too. Dynamite Payson wrote me of his allergy to it, "I just can't breathe any of the dust without half choking." A friend of mine broke out in a rash all over his body plus fever after sanding a plug made of lauan.
The dust generated by sanding cured fiberglass is dangerous and should be kept out of your lungs with a proper respirator. In addition to its own effects, tobacco smoking aggravates the effects of some including coal dust, asbestos and radon decomposition particles.
Polyester resins may contain 35% styrene. OSHA set the average exposure limit for styrene at 50ppm (parts per million) to avoid narcoticeffects. They set the short-term exposure limit at 100ppm to prevent eye and upper respiratory irritation. Its strong odor is detectable down to 0.1ppm if you have just come in from breathing fresh air. Although styrene is a possible human carcinogen, the limit set to avoid narcotic effects is more stringent than that to avoid cancer, based on currently available data.
Also known as lye or caustic soda, it is one of the most hazardous industrial chemicals. You may find it in teak cleaners, bleaches, or some paint removers. While most chemicals can be easily washed off with copious amounts of water, sodium hydroxide reacts rapidly with organic materials such as skin, flesh, and eyes. It causes them to gel and gets absorbed into them so to wash it out is extremely difficult. All the while it continues to burn. I, and others I know, have been drenched with concentrated acids and washed them off in safety showers without injury. The victims I know of caustic spills are badly disfigured or dead. Handle with extreme caution and wear the best eye protection you have.
This solvent is widely used in paints, thinners, paint removers, and other materials boat builders use. The 8hr. average limit for exposure is set at 100ppm in air, and a short-term limit only slightly higher at 150ppm. Avoidance of narcotic effects is the reason. Avoid even brief exposure to high concentrations. Like most solvents, toluene defats the skin and makes it sensitive to dermatitis. For gloves, only Buna-N and nitrile rubber are reasonably impervious to toluene.
Don't use it for cleaning up if you value your skin. It defats the skin and is absorbed through it. It is also probably the most flammable material commonly found in a boat shop. Waterless hand cleaners are better cleaners for your hands.
Cyanides, which are another class of toxic chemicals, are not found in the boat shop. Isocyanates are components of linear paints used for slick hull finishes. They appear to be the most potent sensitizers around. They cause cross-sensitization with other materials. Sensitization shows up as respiratory problems, which may not go away after exposure stops.
The OSHA 8hr. limit for toulene diisocyanate is 0.005ppm (5 parts per billion) and the short-term is 0.02ppm. This means you spray only with a full protective suit and an external fresh air supply. No respirator cartridges protect you.
Some people have the idea that only synthetic compounds are harmful and naturally occurring materials are harmless. Have you ever tumbled in a bed of poison ivy or tangled with a Portuguese man-of-war? Wood dust may well be the worst hazard boat builders encounter because of its potentially toxic nature and its presence in nearly all boat building operations. Turpentine is as toxic as most solvents and stuffing a rag wet with it in your pants pocket can give you a chemical burn in a hurry. Pine tar, like all materials that have been overcooked contains pyrenes, strong carcinogens. If your diet is heavy char-broiled steaks and blackened redfish, you are being exposed to pyrenes.
What's a Boat Builder to Do?
The best all-around advice that might be found in product literature is: "None of our products is safe. They cannot be made safe. Work cleanly."
Get material safety data sheets when you buy materials. They are difficult for someone without chemical background to understand, but there is always useful information on how hazardous the materials are, how to handle them safely, what protective equipment is needed, first aid, and contacts for help in an emergency situation.
Always stop and think about how you are doing a job and how you may get into trouble.
How To Get Help From Material Safety Data Sheets
The information required in MSDS is generally specified by OSHA. The specifics, level of detail, and the manner of presentation are left up to the manufacturers and distributors; for the same chemical, different sources will publish MSDS that are quite different in format though the underlying data will be the same.
The sheets may be incomprehensible at first glance to persons without some knowledge of chemical and physical principles and the descriptive jargon of toxicology and chemical hazards. The information is presented in a standard order and the boat builder should look for:
- Distributor: There will be at least an emergency telephone contact for medical help.
- Material Identification: The chemical nature of the material.
- Numerical rating of any health, fire, and reactivity hazards. These will be numbers from 0 to 3 where 3 is the greatest hazard. Generally, health and fire are your greatest concerns.
- Components: The lesser materials and impurities present.
- Physical Data: Information on color, odor, taste, and quantitative data, which can tell you a lot about hazards of working with the material.
- Vapor Pressure: This number tells you a great deal about ventilation requirements and fire hazards. It is given in mmHg (millimeters of mercury) at 20 degrees C. (68 degrees F).
Values for typical materials are: Water, 17; Acetone, 181; Styrene, 6; Epoxy resin, <0.1, Toluene, 22. [In other words, epoxies are less volatile than water.]
These are saturated vapor pressures: what you have in the vapor space over liquid in a sealed and partly filled can. The higher the vapor pressure, the greater the possible toxic exposure, fire hazard and the better ventilation required.
Remember: Protect Your Eyes!
David admits to having 40 years experience with DuPont.
David W Carnell, 322 Pages Creek Dr., Wilmington, NC 28411
Web page: http://www.angelfire.com/nc3/davecarnell/