SCHOOLS - The Perils of
Permanent Marking Pens
If you’re like me, you probably have at least one permanent marker tucked away in your desk and maybe even a box of coloured ones stashed elsewhere. These pens are great because they’ll write on any material and won’t wash off. But unlike their safer water-based cousins, which will wash off, they are organic solvent-based. And that’s the problem. When was the last time you asked yourself “what could be the health impact of a lifetime of exposure to organic solvents?” The answer, according to Joseph Rodricks in his book Calculated Risks, is “slow poisoning.”
There isn’t enough solvent in a marking pen to act as a fast poison or we’d all be dead. But all organic solvents are toxic under the right conditions and can cause adverse health affects. Are you at risk? To decide this you must know, first, what kinds of injury can result; second, how much exposure over time will put you at risk; and third, what the possible exposure conditions are.
The organic solvents lurking in permanent markers are either the aromatic hydrocarbons toluene and xylene or methyl alcohol. Breathing in too much of these is a concern (inhalation is the main route of entry), and so is using these pens to write on your skin (Hey! Don’t roll your eyes, people do this). Xylene, toluene and methyl alcohol can all be absorbed right through intact skin. If you have to choose among these, alcohol-based markers are safer than those containing aromatic hydrocarbons. They still, however, produce vapours that may cause adverse health effects.
These solvents are central nervous system depressants. At low doses, they produce headaches, nausea, vomiting and dizziness. In large amounts, exposure to toluene and xylene may cause narcosis (drowsiness) and damage to the upper respiratory system, kidneys and liver. They may also irritate your eyes and mucous membranes. Both toluene and xylene are especially irritating to the skin because they dissolve its waxy layers, thereby increasing absorption and causing local irritation.
Xylene is toxic to an embryo or fetus at doses that are not toxic to the mother. You find this kind of information on a material safety data sheet under the teratogenicity and embryotoxicity section. Oh, by the way, under this section it also says that there is insufficient information but, well, xylene may also reduce fertility.
But here is the crux of the slow poisoning concern: with repeated or prolonged exposure to organic solvents you may develop allergies or become chemically sensitive. Here is how it happens. Although you may not have any physical reaction the first time you are exposed to a substance, your body is nevertheless sensitized to it so that you do react on subsequent exposure. The cause of the allergic response is often not readily identifiable. Multiple chemical sensitivities develop over time as a result of doses far below the standards set for protection of the general population, usually as a result of some initial acute exposure. At the present time, such sensitivities affect approximately 10% of the population, and scientists predict that the number of people affected will increase.
Standards have been set for maximum exposure to these solvents over an eight hour working day. Supposedly, these standards protect most adults. They do not, however, apply to children (Health and Welfare Canada says that permanent markers are not to be used by children under 12), old people, pregnant women or people with pre-existing health problems like asthma, all of whom are at greater risk. Exposure standards also don’t take into consideration multiple chemical exposure or whether you have had previous exposure and, if so, at what dose.
When you are assessing whether you are at risk you should also consider other conditions under which you might be exposed to these solvents. For example, toluene and xylene are two of the chemicals that modern building materials off-gas. Regularly spending time in rooms filled with tobacco smoke may expose you to xylene. Even gassing up your car may lead to exposure since premium unleaded gas has anywhere from 10-22% xylene. According to the US International Trade Commission, Canada produced 345 thousand tonnes of xylene in 1987, while the US produced 2772 thousand tonnes (production quantities of toluene are similar). Xylene is used to manufacture a wide range of products, from perfume to plastic. Toluene, like xylene, is contained in a long list of consumer products from nail polish to paint thinner. What does all this mean? It means that your marking pens may not represent your only exposure to these solvents.
How much exposure to these solvents will produce adverse health affects? Are you at risk? Every individual is different and these are not easy questions to answer. But if you’re like me, you’ll never look at permanent markers the same way again. You may even switch entirely to water-based pens...and hope it doesn’t rain.
Lynda Cuddy is an art safety consultant in Vancouver, British Columbia.
Reprinted with permission
from Green Teacher, Dec. 93/Jan. 94, 95 Robert Street, Toronto, Ontario
M5S 2K5, 416-960-1244.