OSHA’s definition of a “mist” vs. science

“The term mist is applied to liquid suspended in the atmosphere. Mists are generated by liquids condensing from a vapor back to a liquid or by a liquid being dispersed by splashing or atomizing. Aerosols are also a form of a mist characterized by highly respirable [they mean breathed - respiration does not need lung in strict biological terms], minute liquid particles.”

First, the OSHA author confuses respiration with breathing. While the term "respiratory protection" is often used to refer to protective masks, respiration and breathing are not the same. Respiration is a biological function and it does not have to take place in a lung. Next, the word "minute" is vague and unscientific. While you can see a mist in the harbor and describe as such in standard prose, you need to be more accurate than that when it comes to describing whether a worker is being exposed to a mist in scientific terms. 

Ambient temperature, pressure, humidity of the air and the size of the particle in the mist as well as the composition of the material are all very important to determine how harmful the mist is and whether it qualifies as a mist.

Mists change as ambient temperature changes. A mist can be described generically as micron sized droplets that are suspended in air for a long period because they are not large enough or heavy enough to settle by gravity. Their size changes all the time. As temperature rises, the droplet evaporates and becomes a gas, so it disappears and may no longer be as noxious. As temperature drops particles may coalesce, like rain in clouds, making the mist disappear. For example, a mist of steam in a steam room could cause some people to cough because they are breathing in micron sized liquid droplets of water, which interfere with lungs function, like when a person drowns. However, when cold air is allowed in the room, water droplets coalesce and form large drops and fall to the floor or attach to walls. The air clears visibly. What remains is water vapor or humidity in the air, and no longer causes harm to the lungs. 

Some mists are so fine that they don't coalesce or settle easily and may remain in the air for a long time. These mists are often referred to as fogs. Foggers are used commercially to deliver insecticides.