I've been filling planter boxes (PB5s to PB12s) with organic soil mixes, with a tiny amount of synthetic fertlizer.

Is this bad for my lungs? The environment wasn't windy, and the soil was moist enough so that any airborne dust was unnoticable, however I've found very fine particles turning my mucus black after work. I was unable to wear a mask for other reasons.

I'm not sincerely concerned with this due to the brevity of the job, however i'm wondering from a theoretical perspective if this would ever be an issue if I held the job long enough? Could it be carcinogenic or reduce lung capacity as it blocks alveolae?