for calculating CDI Health risk assessment for formul: CDI ingestion concentration is calculated mg/kg. but concentration in PM is μg/m3. how to μg/m3 convert to mg/kg for calculating elements of PM in atmosphere?
Depending on the desired accuracy, you can use the "standard atmosphere" sea level value of 1.225 kg/m3 (T=15C, P=1013.25 mb, dry air).
Otherwise, you will require atmospheric pressure, air temperature, and relative humidity at the time of the PM measurement to plug into the gas law:
density = MP/(R*T), where M is the mean molecular weight of air (as adjusted for humidity), P is atmospheric pressure, R* is the universal gas constant, and T is the absolute temperature. Make sure you use metric units. The following should help:
One additional complication is the accounting for the filtering losses in the airway and the PM concentration in the exhaled breath.
If I am getting your question well, you are asking how to convert the atmospheric pollution (c, in mcg/m3) to human exposure in mg/kg. It should be noted that the exposure in mg/kg is in fact dimensionless and is equal to ppm (10-6).
This conversion is dependent on many assumptions, but in general it goes like this:
Let's start with the volume of air inhaled (v, L) per breath, the breathing frequency (n/min), and the period of time (T, min) - this is relatively easy (but you need some assumptions of the type of work, i.e. how the person will be breathing), then the volume V is V=v*n*T/1000 (m3). (1000 converts L to m3)
Now the inhaled amount of the contaminant is m = c*V (mcg) and the exposure E in mg/kg follows as
E(ppm) = m/1000/bw, where bw is the body weight in kg and 1000 converts mcg to mg.
There might be some ready made conversion factors available on the web, my first try would be OSHA or some other occupational health agency.
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