With regard to airborne contagion, an N95 can protect you from contagion, lesser masks protect others from your possible contagion somewhat.
I have a friend who makes granite, quartz, and limestone counter tops, and he and his crew are required to wear N95 while cutting and shaping to prevent silicosis.
I'm not sure what minimum level of mask is recommended to prevent baker's lung, but an N95 will do the job for sure.