Measurement and modelling human dermal bioavailability of potentially harmful organic soil contaminants...by Jack Lort

I am a PhD student who recently started a NERC and BBSRC funded studentship through the STARS Centre for Doctoral Training, working with Prof Paul Nathanail, Dr Christopher Vane and Dr Darren Beriro. Prior to starting my PhD, I studied at Aberystwyth University, gaining a first class degree in BSc Environmental Earth Science and then continuing onto study MSc Environmental Monitoring and Analysis, which I completed in September. These two courses focused heavily on geochemistry, laboratory techniques and contaminated land.

One aim of my PhD project will be to standardise an in vitro method for quantifying the dermal absorption of polycyclic aromatic hydrocarbons (PAHs) from soils. The project is currently very relevant to the UK, as PAHs are commonly found in elevated concentrations within the soils of brownfield land, especially sites such as former gasworks where PAHs are formed through the incomplete or inefficient combustion of organic materials. There is over 660km² of brownfield land in England alone, which is larger than the area of the Greater Manchester Built-up area (630km²) which includes: Manchester, Bolton, Stockport, Oldham, Rochdale, Salford and Bury. The Government aims for at least 60% of new builds to be on brownfield land.

What is Dermal Absorption?

The skin is comprised of three principle layers: epidermis, dermis and hypodermis. The Stratum Corneum is the outermost layer of epidermis which is a protective layer to protect underlying tissues. There are four major pathways for a compound to be absorbed through the skin: intercellular (between cells), transcellular (through cells) and two fissure pathways, via hair follicles and sweat glands. There is a distinct difference between the bioavailability and bioaccessibility of a compound. Bioavailability is the proportion of the total concentration of an organic compound in soil that, following exposure, is absorbed into any part of the skin that then may remain local, or be potentially available for uptake by the blood compartment or tissues for storage, release and distribution to one or more target organs. Bioaccessibility is the total amount of a substance available for absorption, which can therefore be used to estimate bioavailability.

What is dermal absorption?

What Are PAHs?

PAH’s are hydrocarbons composed of multiple aromatic rings (organic rings with delocalised electrons) and are hydrophobic (repels or fails to mix with water) and lipophilic (dissolves in lipids or fats) in nature. Although they can be volatile and water-soluble as low molecular-weight hydrocarbons (< 3 rings) such as benzene. PAH have the tendency to bio-accumulate in plant and animal tissues and are a risk to human health as some are known to be mutagenic and carcinogenic. Although there are over 100 PAHs, the US Environmental Protection Agency (USEPA) 16 are commonly analysed to assess PAH levels to reduce lab costs and to allow long term trends to be easily identified. Of these, benzo[a]pyrene is the most common marker, due to its highly carcinogenic nature.