The pen comes with a MSDS sheet that outlines possible risks associated with the chemical.
Its hazard rating is Toxicity:2 Flamability:2 Reactivity: 1, with 2 = moderate, and 1 = slight.
Inhalation: Repeated inhalation of concentration above permissable exposure limits may result in severe or permanent toxice [sic] effects.
Eye: May cause severe eye irritation, burning, blurred vision.
Skin: Prolonged or repeated contact ca [sic] cause moderate irritation, defatting, dermatitis.
Oral: May result in severe or permanent toxice [sic] effects.
You shouldn't worry too much about fumes from it because it hardens and then doesn't really fume. Additionally, it shouldn't get hot enough on the surface of the chip to cause fuming.
Basically, don't sniff it, eat it, or touch it alot, and you'll be ok.
p.s. - Isn't it kinda scary that there are misspellings in the MSDS data sheet?