Hi Robert

There a number of papers on this subject that you can access from the web iwth levels being found in soem between 1 - 2 mg/m3. A lot comes down to the type of tree being cut and even the type of chain selected, how it is filed as to what exposure level can be found. https://www.mdpi.com/1999-4907/8/12/464/htm is one such paper. You can find a lot more peer reviewed papaers on the system

How much dust comes off a chainsaw? its mostly chips isn't it?
Also, time exposure may mean that the actual exposure level is low.

Although, given the recent reduction in allowable exposure limits it may be required.

The most hazardous fractions of chain saw dust will not be visible to the human eye. At best we can see particles down to 40µm. Particles less than 10 µm are gong to have health effects. The amount of ultra fines particulate which is a risk to health is likely to be elevated. This will be contributed to by the dust from cutting as well as the exhaust from the engine and the oil use to lubricate the blade. (which can get hot).

There was a time that people worked on a roof with no edge protection at all. Or you could smoke when on a plane. Times have changed. There is a high chance that aborists and forestry workers are unaware of the risks to health. In an industry where there are quite a few deaths and acute injuries I guess the focus is on these to start with.

Not being an expert in dust sampling and measurement I would take a dose of practicality here.
I am anticipating that arborists and forest workers are generally operating chainsaws on fresh live timber that has a relatively high moisture and sap content. Much like our regulator advice for wet cutting practices while working with products containing silica, these workers get a natures equivalent for dust suppression.
The simplest way is to undertake some measurement and prove or disprove that an issue exists.

This may be a useful paper to start off on (https://iforest.sisef.org/contents/?id=ifor2123-009). They took 100 samples of forest workers carrying out chainsaw activities. Results for the various tasks are below:
Clear cut in coppice (n=20): GM 1.98 mg/m3 (Range 0.95-5.58 mg/m3)
Thinning (n=23): GM 0.99 mg/m3 (Range 0.38-3.59 mg/m3)
Pruning (n=28): GM 1.36 mg/m3 (Range 0.11-5.40 mg/m3)
Sanitary cut (n=29): GM 1.07 mg/m3 (Range 0.31-2.58 mg/m3)

This is the perfect argument for exposure monitoring. Different environments, different chainsaws, different timbers, and even different operators and work practices are all factors that will affect actual exposure. Where there is any uncertainty about whether or not the WES may be exceeded you need to get some exposure monitoring done. If you don't measure it using credible methods - you can't possibly know what the levels will be!