Most vermicomposting resources (Worm Girl included) recommend using shredded newspaper as worm bedding. It’s free, readily available, holds moisture and provides a carbon-rich food source for the worms. And it is generally thought to be non-toxic. At least a lot of websites and blogs say it is but I wanted to hear it from a reliable source. Or at least a source that refers to scientific data. I checked the Montreal Gazette website and I didn’t find any claims that their print version is non-toxic. Surely if that were so they would want the world to know it. Right? So I asked around. Given all the newspaper that goes into my bins, the compost I harvest probably contains a lot of ink so I wanted to know for sure.
All the Gazette would tell me is “Our ink is vegetable oil based, and contains no toxic properties” (so why don’t they say so on their website?!).
Jean Deneault at Transcontinental, the company that prints the Globe and Mail and La Presse, was a little more helpful:
“Our ink suppliers for newspaper printing and flyer printing have confirmed that they don’t use toxic products to manufacture their inks. For the cold-set printing, the inks are 40% soya base, while the heat-set printing inks are 8% soya base. We distribute flyers that are sometime not printed by our company and we cannot comment on the inks that these printers would use. Any printed products with a large amount of metallic ink coverage could have traces of copper or zinc. Black or other colored pigments should not affect the quality of the compost.”
I was satisfied that the newspapers I feed my worms are safe. It’s also good to know that flyers and advertising supplements are not so safe. I continued my reasearch just to learn more about vegetable oil-based inks. All inks are made by suspending pigments and small amounts of other additives in oil. Old school inks are petroleum-based. Vegetable oil-based inks are usually made with soybean oil.
The soy-based inks are less-toxic but not non-toxic. That’s because the soy-based inks contain the same pigments and other additives as the old inks. However, soy-based ink is brighter and spreads better so less is needed to print each paper. Therefore, there is less ink in newspapers printed with soy-based ink.
The pigment in black ink, which is the most abundant ink in newsprint, is Carbon Black – basically powdered elemental carbon. Although it can be an irritant to the lungs if inhaled the EPA has compiled sufficient evidence to convince me that it is not toxic to me or my worms.
There is less information out there on the toxicity of the pigments used in colored inks. However, according to the Ohio State University the pigments in ink are many of the same pigments used in tattoos and cosmetics:
Phthalocyanine blue CAS 147-14-8
Lithol Rubine magenta CAS 5281-04-9
Diarylide yellow (I couldn’t find any safety data on this one)
