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31 nation. Zero-tolerance policies may increase compliance effect of hair testing, which can detect prior drug use for up with drug and alcohol regulations by establishing stricter to 90 days. J.B. Hunt also tests oral fluids following some and immediate consequences after a single violation. They accidents. Continental Airlines may use blood for follow-up also limit the need for return-to-duty and follow-up testing, tests. Trailways may use blood for postaccident tests and for providing more time, effort, and funding for random testing. some confirmation tests. These policies, however, appear to violate the spirit of the original intent of the policy, which is to provide a "helping BNSF uses hair testing for pre-employment drug hand" to violators. screening for job applicants. Hair testing occurs in addi- tion to the FRA- and FMCSA-mandated pre-employment urine drug test at the job candidate's medical examina- PRE-EMPLOYMENT ALCOHOL SCREENING tion. BNSF company requirements may also vary by state. In Minnesota, BNSF requires a blood specimen when an As previously discussed, pre-employment alcohol screening employee has a BAC of 0.020 and higher on a company- is optional, rather than mandated by DOT, because alcohol is mandated (non-DOT) breath alcohol test. Nebraska law not an illegal substance and no illegal act is performed if the requires that the railway company obtain a blood sample applicant has not yet been involved in safety-sensitive duties. from the employee on a positive company authority test One of the seven surveyed companies uses pre-employment 0.020 and above if requested by the employee at the time alcohol testing. Trailways, an independent group of more of the test. than 80 privately owned motor coach companies, imple- ments alcohol tests as part of its pre-employment screening. BNSF may also use DOT-approved saliva tests for ini- Pre-employment alcohol tests are an inexpensive way to tial alcohol screening. If positive, then the employee must be identify applicants who most likely have alcohol addiction screened and confirmed using an Evidential Breath Testing and cannot abstain from drinking. (EBT) device. Oral fluid tests were noted to be beneficial for screening employees with complex pulmonary medical histories contributing to inadequate breath supply. PRE-EMPLOYMENT BACKGROUND CHECK The use of alternative specimens has elicited consider- Companies may choose to investigate an applicant's drug- able controversy because of many unresolved scientific, and alcohol-testing history for more than the required mini- logistical, and legal issues. A summary of some of the main mum of 2 to 3 years. Trailways, for example, checks past scientific and technical issues is presented in the following test records for up to 5 prior years for potential employees in sections, which are based in large part on the following pub- safety-sensitive functions. lications: Baselt and Cravey (1995), Verstraete (2004), Cone et al. (2007), Kintz et al. (2007), Bush (2008), Gallardo and Queiroz (2008), and Drummer (2010). The reader is encour- ALTERNATIVE SPECIMENS aged to refer to them for additional material. Although the FRA requires both urine and blood tests fol- Since DHHS proposed in 2004 to establish scientific and lowing an accident, urinalysis is the basis of the DOT drug- technical guidelines for the testing of hair, sweat, and oral testing program. Use of alternative specimens, however, has fluid in addition to urine, considerable efforts have been been gaining momentum, with several companies using hair, made in this area of research. Table 24 shows the DHHS pro- oral fluids, and sweat testing in addition to testing urine and posed initial screening and confirmatory cutoffs for alterna- blood. Among the companies sampled for this project, J.B. tive specimens, as reported by Bush (2008). It can be noted Hunt, Continental Airlines, Trailways, and BNSF reported that decisions about what testing methods to authorize are making use of alternative specimens. Note that alternative the province of DHHS, not DOT, and that DOT has no legal specimens are collected based on company-only policies, authority under the Omnibus Act to permit or require types not DOT-regulated testing. of testing that DHHS has not incorporated into its manda- tory guidelines. As one of the largest transportation logistics companies in North America, J.B. Hunt oversees thousands of employ- Blood ees, many with safety-sensitive functions. J.B. Hunt has been using hair testing since May 2006, and it is now used for all Blood drawing is an intrusive procedure and is not often per- pre-employment tests for all employees, not just the safety- formed for the purposes of workplace drug testing. Blood, sensitive population. Approximately over 80% of J.B. Hunt's however, is the primary mode of entry of drugs and metab- drivers had a hair test by September 2010 for that year, and olites into hair, sweat, and oral fluid. It provides the most the company had observed a decrease in the rate of positive direct evidence of the presence of a drug in the system and urine tests by about 75%. They attribute this to the deterrent allows estimation of its likely behavioral effects.

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32 TABLE 24 DHHS PROPOSED INITIAL SCREENING AND CONFIRMATORY CUTOFFS FOR ALTERNATIVE SPECIMENS Hair (pg/mg) Oral Fluid (ng/ml) Sweat Patch (ng/patch) Urine (ng/ml) Drug/Analyte Screen Confirm Screen Confirm Screen Confirm Screen Confirm Marijuana metabolites 1 50 Marijuana (parent) 4 4 THC (parent drug) 2 1 THCA (metabolite) .05 15 Cocaine Cocaine metabolites 500 20 25 150 Cocaine 500a 8b 25b Benzoylecgonine 50 8 25 100 Cocaethylene 50 Norcocaine 50 Opiate Metabolitesc 200 40 25 2,000 Morphine 200 40 25 2,000 Codeine 200 40 25 2,000 6-Acetylmorphine 200d 4 25 10 Phencyclidine 300 10 20 25 Phencyclidine 300 10 20 25 Amphetaminese 500 50 25 500 MDMA 500 50 25 500 Amphetamine 300 50 25 250 Methamphetamine 300f 50g 25g 250h MDMA 300 50 25 250 MDA 300 50 25 250 MDEA 300 50 25 250 a Laboratories are permitted to initially test all specimens for 6-acetylmorphine (6-AM) using the appropriate cutoff for each matrix. b Methamphetamine is the target analyte. c BZE/cocaine ratio 0.005 or cocaethylene 50 pg/ml or norcocaine 50 pg/ml. d Specimen must also contain morphine at concentration 200 pg/mg. e Must contain amphetamine 50 pg/mg. f A confirmatory test must be performed for either cocaine or BZE. g Must contain amphetamine LOD. h Must contain amphetamine 100 ng/ml. Each drug has specific absorption, distribution, metabo- tion to decrease by one-half. Table 25 reports the half-lives lism, and excretion characteristics. Absorption refers to of various illegal drugs. the rate at which a drug enters the bloodstream, which can be affected by the route of administration (i.e., oral inges- In this document, detection time is defined as the time tion, inhalation, insufflations, and injection). After a drug a product can be detected after it was taken. The detection is absorbed into the bloodstream, it circulates through the time for a specific drug depends on several factors: the route body and is distributed in various body tissues. Equilibrium of administration, the pharmacokinetic properties of the is reached when the drug concentration in plasma is equal drug, the metabolism of the individual, the drug dose, and to the drug concentration in tissues. After equilibrium is the drug test cutoff selection. Table 26 reports typical detec- reached, the blood drug concentration diminishes because tion times of selected drugs in blood, serum, or plasma. of metabolism and elimination. The liver is the major site of drug metabolism. In the body, drugs are metabolized into Urine other compounds--some psychoactive, some not--that can have different properties than the parent drug. Drugs and As the blood is pumped by the heart through the system, it their metabolites can be excreted through urine, feces, bile, goes through the kidneys at a rate of 1,200 ml per minute. saliva, sweat, hair, and other pathways. As blood goes through the kidneys, electrolytes, nutrients, and water are returned to the bloodstream, whereas excess Blood is composed of plasma and several kinds of cells water, waste products, and drugs and their metabolites (red blood cells, white blood cells, and platelets). The serum continue to the tubes that propel urine from the kidneys half-life is the amount of time required for a drug concentra- to the urinary bladder. Because some of the water in the

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33 blood is reabsorbed by the kidneys, the concentration of from study to study, depending on the experimental proto- drugs and their metabolites is higher in urine than in the col. Table 27 shows urine drug detection times as reported kidneys. A healthy adult produces from 1 to 2 L of urine by Verstraete (2004). Note the distinction between detection per day. time and maximal detection time. Table 28 shows urine drug detection times as reported by Moeller et al. (2008). In gen- eral, the window of detection for most drugs is 2 to 3 days. TABLE 25 HALF-LIVES OF SELECTED DRUGS AND THEIR A positive urine drug test indicates only that the person METABOLITES has used the drug and cannot be used to determine whether Drug Analyte Half-Life the person is under the influence of the drug. Marijuana Tetrahydrocannabinol 30 min Delta-9-tetrahydrocan- Infrequent users: 2057 h One of the advantages of urine drug testing is that it has nabinol-9-carboxylic acid Frequent users: 313 days been examined extensively, is scientifically proven, and is forensically defensible. Entering the keywords "urine drug Cocaine Cocaine Intravenous: 3741 min testing" in PubMed and limiting the search to humans Smoked: 5889 min yielded 3,575 results. It is a mature technology that is toxico- Intranasal: 73207 min logically accurate and reliable. Benzoylecgonine 6h Opiates Morphine 23 h Oral Fluid 6-Acetylmorphine 625 min Phencyclidine Phencyclidine 746 h Oral fluid consists of saliva, gingival fluid, and cellular debris. Saliva is produced by the salivary glands, which are Amphetamines Amphetamine 734 h highly vascularized. Therefore, drugs in plasma are rapidly Methamphetamine Oral: 10.1 h distributed to the salivary glands. Relative to plasma con- Intravenous: 12.2 h centrations, drug concentrations in oral fluids depend on MDMA Methylenedioxymetham- 7.6 h the water and lipid solubility of the drugs and their metabo- phetamine (MDMA) lites. Table 29 shows drug detection times in oral fluids as Methylenedioxyamphet- 1618 h reported by Verstraete (2004). Note that the drug detection amine (MDA) window in oral fluid is similar to that of blood. Methylenedioxyethylam- N/A phetamine (MDEA) Entering the keywords "saliva drug testing" and "oral Note. Half-life rates obtained from Baselt and Cravey (1995), Burns et al. fluid drug testing" in PubMed yielded 558 and 396 results, (1998), Mas et al. (1999), Couper and Logan (2004), and Verstraete (2004). N/A = not available. respectively. One of the advantages of oral fluid drug test- ing is that drug concentrations can be related to plasma-free TABLE 26 DETECTION TIMES FOR SELECTED DRUGS IN BLOOD, SERUM, OR PLASMA Dose (mg) Route of Analyte Cutoff Detection Drug Administration (ng/ml) Time (h) Marijuana 34 Smoked Tetrahydrocannabinol (THC) 10 5 Delta-9-tetrahydrocannabinol-9-carboxylic acid (THCA) 10 36 Cocaine 100 Intranasal Cocaine 10 12 Benzoylecgonine 10 48 Heroin 1220 Smoked Morphine 1 20 Amphetamine 6 Oral Amphetamine 4 46 Methamphetamine 22 Smoked Methamphetamine 3 48 MDMA 100 Oral MDMA 20 24 Note. Adapted from Verstraete (2004). Urine drug levels vary as a function of the pharmacoki- drug concentrations and to the pharmacological effects of netic properties of the drug, the metabolism of the individual, the drugs (Gallardo and Queiroz 2008). Also, oral fluid can the drug dose, the drug test cutoff selection, and the quantity be easily collected in a fairly noninvasive fashion, under and frequency of the voids before collecting the specimen. direct observation, which reduces the probability of adul- Detection times in the scientific literature, therefore, can vary teration and substitution.

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34 TABLE 27 DETECTION TIMES FOR SELECTED DRUGS IN URINE Dose (mg or THC) Route of Analyte Cutoff Detection Maximal Drug Administration (ng/ml) Time (h) Detection Time (days) 1.75 Smoked Delta-9-tetrahydrocannabinol-9- 15 34 95 Marijuana carboxylic acid (THCA) 3.50 Smoked Delta-9-tetrahydrocannabinol-9- 15 87 carboxylic acid (THCA) Cocaine 100 Intranasal Benzoylecgonine 1,000 4872 22 Heroin 1015 Intravenous, Morphine 1154 11.3 Smoked Amphetamine 9 Methamphetamine 10 Oral Methamphetamine 2.5 87 51 6 MDMA 100 Oral MDMA 20 48 Source: Verstraete (2004). One disadvantage of oral fluid drug testing is that TABLE 28 recently consumed drugs can leave residual amounts in the DETECTION TIMES FOR SELECTED DRUGS IN URINE mouth. The effect and duration of oral contamination have Drug Time not been established, and it is unknown whether this can be Marijuana Single use 3 days overcome by a realistic observed wait period. Furthermore, Marijuana Moderate use, 4 times per 57 days possibly a second disadvantage is that people are sometimes week unable to produce enough oral fluid for analysis (Gallardo Marijuana Daily use 1015 days and Queiroz 2008). Marijuana Long-term heavy smoker More than 30 days Oral fluid, however, has been gaining prominence as Cocaine 24 days Metabolites an alternative matrix for monitoring drugs of abuse in law Opioids Codeine 48 h enforcement and criminal justice purposes, driving under the influence of drugs programs, and treatment settings Heroin (morphine) 48 h (Schwope et al. 2010; Vindenes et al. 2011). Its role in traffic Hydromorphone 24 days safety is likely to increase in the coming years. Methadone 3 days Morphine 4872 h Hair Oxycodone 24 days Hair follicles are highly vascularized, and as the blood circu- Propoxyphene 648 h lates, drugs are absorbed into the growing hair. The growing Amphetamines Amphetamine/ 48 h phase, the antegen phase, lasts 2 to 6 years. Blood supply to Methamphetamine the hair shaft stops during the catagen phase, which lasts Phencyclidine 8 days 1 to 2 weeks. The final stage when the separation from the Source: Moeller et al. (2008). blood supply is complete is known as the telogen stage or the resting phase. Approximately 2% to 3% of head hair is TABLE 29 DETECTION TIMES FOR SELECTED DRUGS IN ORAL FLUID Dose (mg) Route of Administration Analyte Cutoff Detection Drug (ng/ml) Time (h) Marijuana 2025 Smoked Tetrahydrocannabinol 0.5 34 Cocaine 2542 Intravenous, intranasal, smoked Cocaine 1 512 Benzoylecgonine 1 1224 Heroin 20 Intravenous 6-Acetylmorphine 1 0.58 Amphetamine Oral Amphetamine 10 2050 Methamphetamine 10 Sustained release, oral Methamphetamine 2.5 24 MDMA 100 Oral MDMA 126 24 Source: Verstraete (2004).

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35 in the catagen stage and 10% to 15% in the telogen stage at the hair before analysis. Several decontamination--or wash- any point in time. Therefore, drug concentrations will dif- ing--procedures are described in the literature, but there is fer between hairs within one location and between locations no agreement on which procedure must be used (Pragst and such as scalp hair, pubic hair, and arm or leg hair (Cone et Balikova 2006), whether washing the hair is able to remove al. 2007: Gallardo and Queiroz 2008). For hair drug testing, all potential risks from external contamination (Romano et however, specimens are typically collected from the back of al. 2001; Stout 2007; Ropero-Miller and Stout 2008), and the head. whether variations in washing techniques produce analyti- cal variability (Stout 2007). Washing procedures include Hair testing has received considerable attention in recent organic solvents, aqueous buffers, water, and a combination years. Entering the keywords "hair drug testing" in PubMed of these (Gallardo and Queiroz 2008). and limiting the search to humans yielded 834 results. Because of the nature of hair growth, and the fact that hair is Some laboratories have included analysis of the wash solu- typically exposed to the environment, hair drug testing has tion as a crucial step in the decontamination procedure. After unique sets of advantages and disadvantages. several washes, measurement of a drug in the solution is com- pared with the measurement of the drug in the hair. In general, The main advantage of hair drug testing is the long win- if the drug is detected in the hair and not in the solution, it is dow of detection of drugs, which can extend from weeks to an indication of active drug use, whereas if the drug levels in months, depending on the rate of hair growth and the length the solution vis--vis the hair exceed a given criterion, it is an of hair available for sampling. Another advantage is that hair indication of passive contamination. A summary of those pro- collection is relatively easy and noninvasive, with the oppor- cedures is beyond the scope of this project, but the reader is tunity to obtain additional specimens. encouraged to read the following articles for details: DuPont and Baumgartner (1995), Romano et al. (2001), Schaffer et al. One disadvantage is contamination from the environ- (2002), Cairns et al. (2004a,b), Schaffer et al. (2005); Kintz et ment. There are three known mechanisms for incorporating al. (2007), Stout (2007), Hill et al. (2008), Ropero-Miller and drugs into the hair shaft. The first is from blood. The second Stout (2008), and Tsanaclis and Wicks (2008). is from sweat in the tissues surrounding the follicle, usually after the hair emerges from the skin. The third is from envi- The second step is detection of drug metabolites, specifi- ronmental exposure to the drug. cally those that are unambiguously related to endogenous processing of the drugs. In some cases, ratios of the metabo- Detection of a drug is not sufficient to identify drug lite to the parent drug must be interpreted to report results use because hair may be contaminated by exposure to the (DHHS Proposed Revisions to Mandatory Guidelines for smoked drug and by powder residue from surfaces where Federal Workplace Drug Testing, 69 Fed. Reg. 19,644). The use occurred (Ropero-Miller and Stout 2008). Contami- metabolites may be present in much lower concentrations nation is an issue for drugs that may be smoked, such as than the parent drug (Pragst and Balikova 2006), and their marijuana, cocaine, amphetamine, methamphetamine, and detection requires highly sensitive and specific analytical heroin (Stout 2007). techniques (Gallardo and Queiroz 2008). Recent develop- ments in immunochemical, GC/MS, and especially LC/MS, Several studies have shown that being in contact with a which have allowed lower LODs and LOQs, have made this drug can result in the accumulation of the drug in the hair possible (Barroso et al. 2011; Wada et al. 2010). and result in a false positive. Mieczkowski (1995) found that undercover narcotics officers who had chronic envi- Note, however, that some metabolites are not unambigu- ronmental exposure to cocaine had detectable amounts of ously related to endogenous processing of the drugs. Some the drug in the hair; Koren et al. (1992) found concentra- metabolites (e.g., MDA) are used as a drug themselves tions of both cocaine and benzoylecgonine in hair exposed (Pragst and Balikova 2006), some may appear as congeners to varying quantities of crack smoke in a small, unventi- in the parent drug, and some may be formed by degradation lated room; and Thorspecken et al. (2004) found that in during processing (Hoelzle et al. 2008). The latter is espe- vitro hair exposed to marijuana smoke tested positive for cially true for some extraction methods (Barroso et al. 2011). the drug, depending on concentrations in the air, hair care Thus, criteria for interpretation need to be adjusted for the habits, and cosmetic treatment. specific analytical conditions (Hoelzle et al. 2008). Thus, the issue is not whether contamination can occur, Because of the issue of contamination, the Federal Bureau for which there is broad consensus, but whether there are of Investigation laboratory no longer conducts cocaine analy- ways of discriminating between active use and passive con- ses in hair for most cases involving subjects who have a legiti- tamination. Currently, laboratories use two complementary mate reason to be in contact with cocaine, such as attorneys procedures to minimize the possibility of passive contamina- involved in drug cases, law enforcement officers handling tion. The first is decontamination of hair samples by washing drug evidence, and crime laboratory employees (LeBeau

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36 and Montgomery 2009). As Pragst et al. (2010) point out, and pharmacodynamics of illicit drugs under controlled however, it is unlikely that innocent citizens in their daily conditions, most of the studies cited previously compared environment might contaminate their hair to such an extent the results of hair drug tests of subjects of varying hair that it could lead to cocaine-positive results with the current color without an accurate and dependable reference stan- criteria. When contamination is suspected, they suggest that dard against which the sensitivity and specificity of the hair additional investigation be conducted of nonhead hair, which drug tests could be calculated. Because of this difficulty, is much less prone to external contamination, and that hair researchers have resorted to less direct analytical strategies, analysis continues to be a suitable tool in the majority of appli- comparing hair drug test results with urine drug test results cation fields, including testing for cocaine exposure. The Fed- and/or self-report measures. eral Bureau of Investigation laboratory is actively researching this issue of contamination, and it has expressed the belief that Mieczkowski and Newel (1993), for example, compared it can be resolved by identifying a truly unique metabolite the outcome of hair and urine drug tests for cocaine in White that does not exist in street cocaine and/or through additional and Black arrestees. Urine tests indicated that 35.9% of Blacks wash kinetic studies (LeBeau and Montgomery 2010). and 16.5% of Whites were positive for cocaine, for a ratio of 2.18 (35.9/16.5 = 2.18, Blacks were 2.18 times more likely to A second disadvantage is that hair drug testing cannot test positive than Whites). Hair tests indicated that 62.5% of detect recent drug use. Three to 5 days of hair growth are typi- Black and 36.1% of Whites were positive for cocaine, for a ratio cally required for the hair to emerge from the skin surface. Dur- of 1.73 (62.5/36.1 = 1.73, Blacks were 1.73 times more likely to ing that time, the drug may be detected in the sweat bathing test positives than Whites). Relative to Whites, therefore, pos- the hair, but washing procedures can make detection unlikely. itive cocaine tests for Blacks were more likely with urine tests than with hair tests. Thus, no evidence of a race bias in hair A third disadvantage is that incorporation of the drugs into testing was found. Similar results were obtained by Hoffman the hair is affected by melanin. Studies have shown that mel- (1999) with Black and White applicants for employment with anin content increases with hair "darkness" (Baumgartner a large metropolitan police department. A recent report by and Hill 2001) and that the drug concentration in pigmented Ropero-Miller and Stout (2011) further suggests that whereas hair can be significantly higher than in nonpigmented hair cocaine analyte concentrations may be significantly higher (Kidwell and Smith 2007). Some researchers have further in dark hair types, including African American individuals, suggested that because minority groups tend to have dark use of benzoylecogonine/cocaine ratios and extensive decon- hair, the melanin bias is in effect a race bias. Others have tamination wash criteria greatly reduce positive hair in vitro suggested that differences in hair structures, permeability testing results in contaminated hair. of the hair, use of cosmetic hair treatment, personal hygiene, and artificial hair color may also affect the drug analyses A fourth disadvantage is the interference of cosmetic treat- (Kidwell et al. 2000; Wennig 2000). ment on the analysis of hair. Because of cultural differences in ethnic grooming, some groups tend to wash their hair less Entering in PubMed the keywords "melanin bias in hair often than others. Some researchers have suggested that the drug testing," "race bias in hair drug testing," and various lower frequency of hair washing causes less leaching of the combinations of these yielded 32 articles. Of those, seven drug out the hair as a result of washing, which results in a could not be retrieved and 10 were outside the narrow focus potential increase of positive tests. Conversely, because most of interest. Of the 15 articles that were reviewed, some found cosmetic treatment involves oxidation of the hair, it may that drug levels were higher in darker color hair (Kelly et reduce the availability of drugs for detection in hair testing, al. 2000; Mieczkowski and Newel 2000; Mieczkowski et al. which results in a potential increase of negative tests. 2002; Hill et al. 2005; and Mieczkowski and Kruger 2007), but none of the reviewed articles found direct support for the In summary, although some researchers assert that the race bias hypothesis (Mieczkowski and Newel 1993; DuPont inherent drawbacks of hair testing preclude it for use in the and Baumgartner 1995; Hoffman 1999; Kelly et al. 2000; workplace, where accuracy and fairness in employment Mieczkowski et al. 2002; Tassiopoulos et al. 2004; Bern- decisions are paramount (Romano et al. 2001; Stout 2007; stein et al. 2005; Hill et al. 2005; Mieczkowski and Kruger Ropero-Miller and Stout 2008), others assert that the main 2007; Mieczkowski et al. 2007). The apparent inconsistency analytical problems have been adequately dealt with (Bar- may be explained by the fact that different ethnic groups roso et al. 2011), and it is important that hair preferentially have different patterns of drug use (Kelly et al. 2000) and be chosen for pre-employment and random tests (Pragst and that some analytical procedures remove the melanin by cen- Balikova 2006). trifugation prior to the analysis of keratin, another compo- nent of human hair (Baumgartner and Hill 2001). Sweat It can be noted, however, that because of the logistical Sweat is produced by eccrine and apocrine glands in the skin and ethical difficulties in studying the pharmacokinetics for the purpose of thermal regulation of the body. Drugs are

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37 incorporated into sweat by passive diffusion from blood to higher than urine for amphetamine/methamphetamine, and by transdermal passage across the skin. Entering the cocaine, and marijuana, whereas urine positivity rates tend keywords "sweat drug testing" in PubMed and limiting the to be higher for opiates and phencyclidine. search to humans yielded 147 results. Sweat is typically col- lected with a patch made of transparent film that is attached TABLE 30 to skin. While wearing the patch, sweat saturates the pad and SAME-DONOR HAIR AND URINE POSITIVITY RATES (%) the drugs present in sweat are retained. Drug Hair Urine Overall 12.6 7.6 The main advantage of sweat testing is a relatively lon- ger window of detection, which spans the duration the patch Amphetamines 5.9 2.1 is applied to the skin, usually 1 week, plus 2448 h before Methamphetamine Only 5.9 1.8 the application of the patch. Other advantages are that the Cocaine/Metabolites 4.8 0.65 patch is noninvasive, relatively tamper-proof, and provides a Opiates 0.23 0.52 cumulative measure of drug exposure. Phencyclidine 0.05 0.05 Because it is difficult to estimate sweat volume and to eval- Marijuana Metabolites 3.4 3.4 uate drug concentrations, sweat testing is primarily a qualita- Source: Sample (2010). tive rather than quantitative method of measuring drug use. Disadvantages include low acceptability of patch wearing, the Overall, the pattern of higher positivity rates for hair test- possibility of accidental removal or purposeful removal, and ing is robust. Table 32 reports the positivity rates by type of the potential for contamination at the time of removal. test for urine and hair drug tests for the general U.S. work- force (Quest Diagnostics November 2009). Relative Utility of Different Specimen by Type of Drug Test Mieczkowski (2010) examined 11,242 same-donor paired Does the larger detection window of hair analysis--relative urine and hair specimens for pre-employment tests and to urine analysis--result in higher positivity rates? There is 1,458 urine and hair specimen for random tests. Of the pre- evidence that this may be the case. employment tests, approximately 2% of the urine specimens and 9% of the hair specimens were positive. Of the random Sample (2010) examined 193,000 same-donor paired tests, 0.6% of the urine specimens and 3% of the hair speci- specimens of hair and urine, collected over a 5.5-year period mens were positive. from 2004 to 2009. As shown in Table 30, overall positivity rates for hair were considerably higher than the positivity An important distinction must be made at this point rates for urine. Hair analyses detected use of amphetamines between drug use and impairment. Drug use can be detected (particularly methamphetamine) and cocaine to a greater with a drug test by the presence of active or inactive analytes, extent than urine analyses. whereas impairment can only be inferred by the presence of active analytes and/or behavioral signs and symptoms. As Studies from different donors (independent specimens shown in the previous sections, active analytes tend to have of urine and hair) also show differences in positivity rates shorter half-lives than inactive analytes and can, therefore, between urine and hair, but only for certain type of drugs be detected for shorter periods of time. (Quest Diagnostics November 2009). Table 31 reports the positivity rates by drug category for urine and hair drug tests The suitability of different specimens varies as a function for the general U.S. population (Quest Diagnostics Novem- of the type of test that is being performed. Pre-employment ber 2009). According to these data, hair positivity rates tend tests, for example, are administered to determine whether TABLE 31 POSITIVITY RATES (%) BY DRUG CATEGORY FOR URINE DRUG TESTS AND HAIR DRUG TESTS FOR THE GENERAL U.S. WORKFORCE Amphetamines Cocaine Marijuana Opiates Phencyclidine Year Urine Hair Urine Hair Urine Hair Urine Hair Urine Hair 2005 0.48 2.1 0.70 5.0 2.5 3.0 0.32 0.14 0.020 0.01 2006 0.42 1.1 0.72 4.5 2.4 3.5 0.32 0.14 0.020 0.01 2007 0.44 1.2 0.58 5.3 2.3 3.9 0.35 0.17 0.020 0.01 2008 0.48 0.86 0.41 4.2 2.1 3.4 0.38 0.14 0.020 0.00 2009 (Jan.June) 0.55 1.1 0.30 3.2 2.0 3.2 0.44 0.15 0.01 0.01