asbestos conversion mg/m3 to fb/ml

[georgeroberts]

HI All.

I am a newbies and and I am not a Hygienist, but have occasionally delved into environmental engineering relating to asbestos analysis.

Hoping to get some assistance with a issue that I have often seen - my question is probably suited for an experienced hygienst but i welcome all contributions.

I have seen in past reports/journals (and studies) that a small cut into asbestos fibre cement sheeting with an angle grinder can liberate approx (5fb/ml to 20fb/ml). Similar with drilling a 10mm hole (3fb/ml). These are rough estimates based on PCM analysis.

BUT... I have also seen some publications stating that only "1mg of asbestos" is sufficient to generate 33PCM fb/ml per 1 m3. (Apparently this is a rough conversion used by hygienist). This conversion of 1mg to fb/ml is referenced in some past studies undertaken in the 1980's i believe.

Cutting or drilling into an asbestos sheeting will disturb far more (ie much much more!! ) than 1mg of asbestos...even if one were to assume only 20% of the cement sheeting contained asbestos.

So my question : How can 1mg be stated as releasing 33PCM fb/ml yet cutting or drilling only liberate 5 to 20fb/ml - noting the latter disturbs Orders of magnitude more material.

Many thanks for any help

[Waterbaby]

Bump

WB