Toxic Blog #4 – Human Health Risk Assessment – Chemical Exposure

Physicochemical properties and chemical exposure

In my first Toxic Blog#1, I talked about the way in which vapour pressure data can be used to predict whether exposure is likely to occur by inhalation, but also whether the substance is likely to be environmentally mobile.

In this Toxic Blog#4, I will show you how some basic physicochemical properties can be used to help us predict likely exposure routes, which is an important part of the human health risk assessment work.

Human health risk assessment

As many of you probably already know, human health risk assessment is all about predicting the likelihood of harm occurring to humans when using a specific chemical in a specific activity (e.g. spray painting). Risk assessment can be represented as follows,

Risk = Hazard x Exposure

Therefore, in order to undertake any human health risk assessment work, we need to have information on the hazard (i.e. carcinogen, sensitiser, etc) and exposure (i.e. oral, dermal and inhalation respectively).


‘Without appropriate PPE, even witches will be exposed to the cauldron’s lethal chemical vapours!’   Image:Aldegonde/


How physicochemical data can be used to predict potential exposure routes

As I mentioned in a previous toxic blog, basic physicochemical data, which is typically found in Section 9 of the safety data sheet (SDS), can give us a lot of clues regarding the potential exposure routes (i.e. oral, dermal, inhalation) and even toxicity.

For example, vapour pressure and boiling point give an indication of the likely volatility of the chemical and the likely inhalation risk. (See Toxic Blog #1 for more information)

Water solubility and the partition coefficient (Log Kow ) both can provide an indication of the likelihood of absorption across a biological membrane and bioaccumulation. Specifically, in the absence of any actual test data, this information can be useful in predicting whether skin absorption would occur.

Typically a very low Log Kow value, i.e. less than zero, would suggest that the chemical is too water-soluble to cross the outer layer of the skin. Therefore, in the absence of any other information, we could assume that dermal absorption would be unlikely.




Being able to interpret basic physicochemical data, can help us enormously when undertaking human health risk assessment work, writing SDS and of course classification and labelling for supply and transport.

Upcoming live streaming training courses

Toxicology Training is pleased to announce the launch of three new live-streaming training classes ( 6 hours total – split into three sessions). The early bird discount applies for all course dates (£349/per person).

These brand new Live streaming training classes (6 hours total – split into three sessions) are perfect for anyone who wishes to avoid the current problems/cost of travelling but wants something more substantial than a webinar or eLearning course.

Each class is broken down into three separate 2- hour sessions which are run over the three respective days. This means that your workday is not disrupted and it gives you time to ‘digest’ the material before the next session.

Upcoming SDS related training webinars

Introduction to Toxicology, Ecotoxicology & Physicochemical Properties for Safety Data Sheets  June 23rd 2020.


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