Hair Analysis in Clinical and Forensic Toxicology

Pascal Kintz, Alberto Salomone, Marco Vincenti

• Publisher: Academic Press
• Year: 2015
• ISBN:
  9780128017104
• Topic: Ciencias biológicas
• Subtopic: Investigación y metodología científicas

Hair Analysis in Clinical and Forensic Toxicology is an essential reference for toxicologists working with, and researching, hair analysis. The text presents a review of the most up-to-date analytical methods in toxicological hair analysis, along with state-of-the-art developments in the areas of hair physiology, sampling, and pre-treatments, as well as discussions of fundamental issues, applications, and results interpretation.

Topics addressed include the diagnosis of chronic excessive alcohol drinking by means of ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEE), the early detection of new psychoactive substances, including designer drugs, the development of novel approaches to screening tests based on mass spectrometry, and the detection of prenatal exposure to psychoactive substances from the analysis of newborn hair.

• Unites an international team of leading experts to provide an update on the cutting-edge advances in the toxicological analysis of hair
• Demonstrates toxicological techniques relating to a variety of scenarios and exposure types
• Ideal resource for the further study of the psychoactive substances, drug-facilitated crimes, ecotoxicology, analytical toxicology, occupational toxicology, toxicity testing, and forensic toxicology
• Includes detailed instructions for the collection, preparation, and handling of hair, and how to best interpret results

Chapter 1

Anatomy and Physiology of Hair, and Principles for its Collection

Gail Audrey Ann Cooper, Cooper Gold Forensic Consultancy Ltd, Fife, Scotland, UK

The incorporation of drugs and metabolites into the growing hair follicle provides the basis for a historical record of past use and exposure to drugs. Hair growth rates vary depending on the type of hair and also vary from person to person but using an average head hair growth rate of 1 cm/month allows an estimate of the timescale of drug use/exposure in the months prior to sample collection. The key structures of the anatomy involved in the formation of the hair follicle and incorporation of drugs are described and special attention given to the three main routes of incorporation: from the bloodstream, sweat and sebum bathing the hair, and from numerous sources of external contamination. The mechanisms of incorporation are also addressed focusing on the role of melanin and the question of a dose–response relationship.

Finally, sample collection protocols are discussed in addition to highlighting case-specific differences for workplace drug testing, postmortem investigations, and drug-facilitated crimes.

Keywords

Hair physiology; hair growth; incorporation mechanisms; sample collection; external contamination

1.1 Introduction

The main advantage of hair as a testing matrix is the ability to provide historical detail of an individual’s exposure to drugs following chronic use, but it is also possible to detect drugs in hair following a single exposure [1]. Unlike many traditional biological samples collected for toxicological investigations such as blood, urine, or oral fluid, drugs incorporated into the hair matrix remain relatively stable for many months or even years.

As a consequence of these advantages, hair samples are routinely collected and analyzed as part of criminal investigations (drug-related deaths, drug-facilitated crimes (DFCs), child protection) and for monitoring drug misuse (drug rehabilitation programs, workplace drug testing). The number of laboratories offering hair testing continues to increase and although there are currently no recognized standardized methodologies, the importance of adherence to industry best practice and recognition of the implementation of international quality standards (e.g., ISO/IEC 17025:2005) for testing laboratories who provide this service has been reported [2].

With continual improvement in instrument sensitivity and recognition of the importance of method validity with acceptable detection limits, the main challenges to expert evidence relating to hair testing are not as a result of unsuitable testing methodologies but are most commonly a consequence of over interpretation of the analytical findings. This is invariably due to a lack of understanding of the many factors affecting the presence of drugs in hair and no consideration given to the role of alternative routes of incorporation or indeed the degradation of drugs in hair over time.

Although researchers have reported finding arsenic in hair collected from the Emperor Napoleon Bonaparte [3] and cocaine in the hair of Peruvian mummies [4] centuries after their deaths, drug concentrations in hair decrease over time due to natural wash out [5]. The stability of drugs in hair is dependent on both the morphology and physicochemical properties of hair [6]. On a daily basis, hair is subjected to exposure to sunlight and weathering that has been shown to reduce concentrations of cannabinoids [7], methadone, cocaine and their metabolites, and heroin metabolites in hair [8]. External contamination and loss of drugs from hair is facilitated by diffusion into and out of the hair in the presence of water [9]. Although daily shampooing does not significantly affect drug concentrations [10,11], drying your hair, curling or straightening your hair with heat can damage or destroy the cuticle providing routes for contamination and loss of incorporated drugs.

Further damage is evident when hair is subjected to harsher cosmetic treatments [10,12–16]. Studies reported in the literature are varied with respect to the drugs and cosmetic treatments investigated but are all in agreement that dyeing, perming, relaxing, and bleaching have a deleterious effect on the drug concentration detected in hair. Decreases in drug concentrations were more prominent for bleached hair compared with dyed hair and damaged hair showed significantly lower concentrations.

In order to fully understand and interpret the results of hair tests, it is essential that the forensic toxicologist has a clear understanding of what factors influence the incorporation of drugs into the growing hair shaft including contamination but must also consider the factors affecting loss of the incorporated drug. The focus of this chapter will be on the routes of incorporation and the factors influencing incorporation. This chapter will also address the importance of the sample collection process and will highlight case-type-specific collection protocols to ensure the collection of a representative sample for all toxicological investigations.

1.2 Hair Anatomy and Physiology

Hair covers almost the entire surface of the human body with the exception of the outer surface of the lips, the palms of the hands, soles of the feet, and some parts of the external genitalia [17]. The main purpose of body hair is to protect the surface of the skin from injury and to help regulate body temperature. The appearance of body hair varies from fine almost colorless hair found on most parts of the body surface to thicker, longer hair on the scalp.

The hair shaft, visible above the surface of the skin, consists of tightly packed fully keratinized cells with the cuticle forming an outer protective layer [18]. The cuticle is susceptible to damage from a number of sources including, exposure to light or heat, chemical treatments including bleaching and perming, and also physical damage. As a consequence, over time the surface of the hair may be compromised exposing the inner layers and is particularly evident in the distal ends of the hair.

The interior structure of the hair shaft contains cortical cells forming the cortex which encompasses the bulk of the hair shaft and also contains cuticle cells where melanin, the principle pigment in hair, is located. The innermost region of hair within the cortex is the medulla and may be continuous along the length of the shaft, discontinuous, or completely absent.

The hair follicle is embedded 3–4 mm below the surface of the skin and is the key structure responsible for hair growth. The structure of the hair follicle is illustrated in Figure 1.1.

Figure 1.1 Structure of the hair follicle.

The main structures of the hair follicle include the outer root sheath (ORS), the inner root sheath (IRS), and the root bulb. The ORS forms a bulge area at the base of the erector pili muscle, close to the sebaceous gland and is believed to be the source of stem cells critical for hair follicle development and pigmentation [19]. The IRS provides support for the growing hair producing intracellular binding material and directing the growing hair upward [20].

The cells located within the lower region of the root bulb, the matrix, are mitotically active while the upper region of the root bulb contains the keratogenous region. At the base of the root bulb is the dermal papilla which contains the blood supply. The IRS degrades as the growing hair dehydrates and keratinization takes place [21].

Close to the hair follicle are the sebaceous and apocrine glands both of which secrete directly into the follicle. The apocrine glands, unlike the sebaceous glands, are not present over the entire surface of the body but are localized in the axilla and pubic regions. The eccrine sweat glands are located close to the follicle but secrete near the exit of the hair follicle not directly into the follicle [22].

1.3 Classification of Hair Types

The three basic hair types on the human body are classified as vellus, intermediate, and terminal. Vellus hair covers the majority of the body surface of both children and adults, is fine, short, and non-pigmented, and is also found on the eyelids and forehead. Where vellus hair is produced by non-sexual hair follicles and unaffected by hormones, intermediate and terminal hairs are influenced by hormones and changes during puberty. Terminal hair is found on the scalp, beard, eyebrow, eyelash, armpit, and pubic areas and in contrast to vellus hair is coarse, long, and pigmented with a large cross-sectional area. Intermediate hair has characteristics of both vellus and terminal hairs and is found on the arms and legs of adults.

Human hair is also commonly classified using the ethnic subgroups of African, Asian, or European. An alternative classification system proposes eight different subgroups based on whether the hair is straight or curly and provides a more objective approach than a subjective ethnicity-based approach [23]. The classification system involves the measurement of three parameters: the curve diameter, the curl index, and the number of waves.

1.4 Hair Growth Rates

A number of factors affect hair growth including age, stage of development, sex, pregnancy, metabolic and genetic disorders, nutrition,...