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Testing times

04 May 2014

Paul Powles explains how developments in testing methods are making it easier for employers to establish a robust drugs and alcohol policy.

Using prescribed or prohibited drugs can alter perceptions of the working environment and produce side-effects that can impact the day-to-day activities a person would normally take for granted.  The business impact can be costly and potentially life-threatening, for example, a machinery incident or fatal collision while operating a vehicle.

Hair toxicology tests are becoming increasingly popular with health and safety professionals looking to routinely assess the suitability of individuals employed in safety critical occupations.

Equally, hair testing is used during the recruitment process and pre-employment screening to verify whether an individual is prone to drug use and therefore a suitable candidate for a role.

A brief history of hair toxicology

Analysis of hair has been used as an indicator of drug use for many years, but it is only since the early to mid-1990s that commercial laboratories have started to specialise in hair analysis. The Society of Hair Testing (SoHT), which emerged in 1995 to promote hair testing science and cooperation among its members, has been instrumental in driving the procedures of hair toxicology into a professional domain so that results from tests can be accepted by civil and criminal courts.

Sampling and screening

It is crucial that rigid procedures are in place to ensure accurate results are taken beginning at the point when the sample is first obtained. Results can be given as evidence in civil or criminal court cases and therefore the integrity of the chain of custody of the sample must be infallible.

For sampling purposes, head hair is normally the sample of choice as it can give a historic persepective of drug abuse, growing at an accepted rate of 1 cm per month.  If head hair is not available then samples from other parts of the body, such as underarm hair, chest hair, leg hair and pubic hair, may be sampled but a time line of drug use cannot be applied as it does not grow at a constant rate. Nevertheless, these samples can still provide an assessment of illicit drug absence or presence.

Where possible, the sampling of a pencil thickness of hair is taken from the back of the head just below the crown, as close to the scalp as possible to cause the least aesthetic disturbance for the donor. The sample can then be sent to the lab from anywhere in the world using normal postal procedures; hair samples do not require any special storage facilities during transit, for example, cold storage and or biohazard regulations.

Hair analysis commences by washing the sample with solvent to ensure all possible sources of external contamination are removed.  Drugs are then extracted by solubilising the drugs in a suitable medium to release any compounds from the sample. The extract is then screened to assess the presence or absence of certain drug groups, or analysed by a specific method to detect drugs that are more likely to be present. Any positive samples from the screen are then submitted to compound analysis, using techniques such as gas chromatography-mass spectrometry (GC-MS/MS) or liquid chromatography-mass spectrometry (LC-MS/MS). These instrumental techniques not only provide data on quantitative amounts of compound but also evidence associated with their identity, which is an important consideration when discussing the results in a court of law.

Instrumentation methods have now advanced to such an extent that some commercial laboratories are by-passing the manual screening stage by investing in state-of-the-art Ultra High Performance Liquid Chromatograph Mass Spectrometry (UHPLC-MS/MS) machines. This allows them to process numerous samples at the same time, screening and confirming substances simultaneously while retaining the very sensitive quantification and identification criteria.

Results and expert witness

Interpretation of hair analysis data is usually the responsibility of an experienced expert, who can take many factors into consideration when preparing an Expert Witness Report for judicial review.

Results of analysis are reported as either a Certificate of Analysis (CofA) or Expert Witness Report.  The latter provides an interpretation of results and is structured for court presentation purposes, so this is typically recommended when any interpretation of positive outcomes are recorded.

An experienced forensic toxicologist can provide useful insights into the meaning of the results. Furthermore, as an Expert Witness they can support the case in a court room setting, providing impartial evidence and opinions associated with the purely analytical aspects of the case.


The benefits of hair toxicology for employers are numerous. The practice is now well-established and accepted by justice systems around the world, and its ease of sampling and posting - plus increased turnaround speed for results – makes it an invaluable tool for employers looking to build up a more accurate picture of short-term and historic drug abuse.

Paul Powles is toxicology case manager for laboratories and analytical services at Environmental Scientifics Group.