• Dermal Nanotoxicology
• Sebum Research

The Chemical Toxicology R&D Team is based at the Centre for Radiation, Chemicals and Environmental Hazards in Oxfordshire. The current research interests of the team are centred on dermal (skin) toxicology and nanotoxicology. Our interest in skin arises from the fact that it is continually exposed to the environment and so may be the site of action for many toxic substances and / or a route by which many hazardous substances could enter the body.

Dermal Nanotoxicology

Nanoparticles are groups of extremely small particles which have at least one dimension of less than 100 nanometers (nm).

The use of nanoparticles in a wide range of applications including cosmetics and sunscreens has rapidly expanded in recent years. However, there is little available information of the potential toxicological hazard from exposure to these particles.

This research programme is concerned with investigating the potential of nanoparticles to undergo dermal absorption, including the development of a novel in vitro system for assessing the dermal absorption of these particles.

This research complements other research involving exposure to nanoparticles by inhalation, which is currently being developed at the National Nanotoxicology Research Centre (NNRC).

Urban 'soot' nanoparticles (non-engineered nanoparticles)

Such particles are present in diesel exhaust. Individual particles are of about 20 - 50 nm diameter and are commonly seen to aggregate to produce strings and clusters.

An engineered carbon nanotube

Sebum Research

Sebum is an oily substance which is secreted onto the surface of the skin, particularly in areas such as the forehead.

Previous research within this group has demonstrated the potential of sebum to entrap chemicals from the environment. This research programme is concerned with investigating the use of sebum as a sampling matrix to determine whether an individual has been exposed to a hazardous amount of a chemical in the environment following either accidental or deliberate release.

The research to date has investigated the uptake and desorpton of volatile organic compounds into a film of sebum with methanol and benzene used as model hydrophilic and lipophilic chemicals. Further experiments have investigated the effect of a skin surface sebum layer upon the dermal absorption of these chemicals, to characterise any changes in rate of uptake due to the sebum layer.

These initial studies have demonstrated that sebum has the potential to entrap chemicals present in the environment, with residual detectable levels of the chemicals remaining within the sebum after many hours.

The uptake and desorption of benzene from a saturated vapour into an artificial sebum layer

The uptake and desorption of methanol from a saturated vapour into an artificial sebum layer

There is potential that analysis of samples of sebum taken, for example, by means of a wipe across the forehead, may enable identification and quantification of hazardous chemicals to which individuals may have been exposed.

The benefits of sebum sampling, compared with existing technques such as blood / plasma sampling and urinalysis would be:

• It is non-invasive and simple to perform without the need for medical personnel (as would be required for blood / plasma samples)
• Members of the public who may have been exposed to a chemical would be expected to be more co-operative to sampling by means of a skin wipe than they would be to blood or urine samples
• Samples can be taken rapidly following exposure and this would eliminate the time taken for the chemical to be present at a detectable level in the blood, plasma or urine
• Chemicals present in sebum samples taken from the skin surface would not have been subjected to any significant metabolic processes, facilitating rapid analysis

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