As a dry medium, pastels produce a lot of dust during the working process, which can be inhaled in the lungs and cause respiratory irritation. The popular orange, red, and yellow colors contain cadmium pigments, which may lead to poisoning. Many modern pastels are developed with substitutions for chromium, cadmium, and other toxic components. Artists may also wear face masks (which is quite uncomfortable) or work outside.
The dust from pastel pencil stays mainly on the paper and can be blown off and not breathed in. Even for most people with asthma, using this medium is no problem at all.