Effective cannabis testing protocols for workplace safety in South Africa post legalisation: Navigating the new normal
DOI:
https://doi.org/10.7196/Keywords:
Cannabis Legalisation; Workplace drug testing; Cannabis Testing ProtocolsAbstract
The legalisation of private cannabis use in South Africa presents significant challenges for occupational health, especially in safety- sensitive environments. This article analyses the medical, legal and ethical issues surrounding workplace cannabis use, focusing on the pharmacodynamics and pharmacokinetics of delta-9-tetrahydrocannabinol (THC), the primary psychoactive compound. The recent legal precedent that critiques the effectiveness of zero-tolerance policies is reviewed, and the establishment of per se THC thresholds that are medically and legally sound is proposed. The study advocates for a tailored approach to risk categorisation and testing protocols in workplaces, aiming to support occupational health professionals in developing policies that are effective, ethical and compliant with legal standards.
References
1. Van Niekerk JP de V. Medical marijuana and beyond. S Afr Med J 2014;104(6):387. https://doi. org/10.7196/SAMJ.8335
2. Prince v Minister of Justice and Constitutional Development 2013 Case No: 8760 (WCC).
3. Rubin v National Director of Public Prosecution 2013 Case No: 7295 (WCC).
4. Acton v National Director of Public Prosecution 2012: 31 March 2017, Case No: 4153 (WCC).
5. Amendment to the Schedules of the Medicines and Related Substances Act No. 101 of 1965.
Government Gazette No 43347, May 2020.
6. Amendment to the Schedules of the Medicines and Related Substances Act No. 101 of 1965.
Government Gazette No. 5181, No. 51171, 6 September 2024.
7. Minister of Justice and Constitutional Development v Prince 2018 CCT 108/17 (ZACC).
8. Cannabis for Private Purposes Act No. 7 of 2024.
9. Marasi v Petroleum Oil and Gas Corporation of South Africa (SOC) Ltd (2023) 10 BLLR 1043 (LC).
10. Enever v Barloworld Equipment South Africa, a division of Barloworld South Africa (Pty) Ltd (2024) 6 BLLR 562 (LAC).
11. NUMSA obo Nhlabathi and another v PFG Building Glass (Pty) Ltd and others (2022) JOL 56426 (LC).
12. Fant RV, Heishman SJ, Bunker EB, et al. Acute and residual effects of marijuana in humans. Pharmacol
Biochem Behav 1998;60(4):777-784. https://doi.org/10.1016/s0091-3057(97)00386-9
13. Heishman SJ, Arasteh K, Stitzer ML. Comparative effects of alcohol and marijuana on mood, memory, and performance. Pharmacol Biochem Behav 1997;58(1):93-101. https://doi.org/10.1016/S0091-
3057(96)00456-X
14. Heishman SJ, Huestis MA, Henningfield JE, et al. Acute and residual effects of marijuana: Profiles of plasma THC levels, physiological, subjective and performance measures. Pharmacol Biochem Behav 1990;37(3):561-565. https://doi.org/10.1016/0091-3057(90)90028-G
15. Hart CL, Van Gorp W, Haney M, et al. Effects of acute smoked marijuana on complex cognitive performance. Neuropsychopharmacology 2001;25(5):757-765. https://doi.org/10.1016/S0893- 133X(01)00273-19
16. Kurzthaler I, Hummer M, Miller C, et al. Effect of cannabis use on cognitive functions and driving ability. J Clin Psychiatry 1999;60(6):395-399. https://doi.org/10.4088/jcp.v60n0609
17. Liguori A, Gatto CP, Jarrett DB. Separate and combined effects of marijuana and alcohol on mood, equilibrium and simulated driving. Psychopharmacology 2002;163(34):399-405. https://doi. org/10.1007/s00213-002-1124-0
18. Liguori A, Gatto CP, Robinson JH. Effects of marijuana on equilibrium, psychomotor performance, and simulated driving. Behav Pharmacol 1998;9(7):599-609. https://doi.org/10.1097/00008877- 199811000-00015
19. Raemakers JG, Robbe HWJ, O’Hanlon JF. Marijuana, alcohol and actual driving performance. Hum Psychopharmacol Clin Exp 2000;15(7):551-558. https://doi.org/10.1002/1099-1077(200010)15:7<551::AID- HUP236>3.0.CO;2-P
20. Sexton BF, Tunbridge R, Brook-Carter N, Jackson PG, Wright K. The influence of cannabis on driving. TRL report no. 477. Crowthorne: TRL Ltd, 2000. https://www.researchgate.net/publication/323309551_ Sexton_BF_Tunbridge_RJ_Brook-Carter_N_Jackson_PG_Wright_K_Stark_MM_and_K_ Englehart_2001_The_Influence_of_Cannabis_on_Driving_TRL_Project_Report_477 (accessed 1 August 2024).
21. Pickworth WB, Rohrer MS, Fant RV. Effects of abused drugs on psychomotor performance. Exp Clin Psychopharmacol 1997;5(3):235-241. https://doi.org/10.1037//1064-1297.5.3.235
22. Ramaekers JG, Kauert G, van Ruitenbeek P, et al. High-potency marijuana impairs executive function and inhibitory motor control. Neuropsychopharmacology 2006;31(10):2296-2303. https://doi.org/10.1038/ sj.npp.1301068
23. Menetrey A, Augsburger M, Favrat B, et al. Assessment of driving capability through the use of clinical and psychomotor tests in relation to blood cannabinoids levels following oral administration of 20 mg dronabinol or of a cannabis decoction made with 20 or 60mg Delta 9-THC. J Anal Toxicol 2005;29(5):327-338. https://doi.org/10.1093/jat/29.5.327
24. Janowsky DS, Meacham MP, Blaine JD, et al. Marijuana effects on simulated flying ability. Am J Psychiatry 1976;133(4):384-388. https://doi.org/10.1176/ajp.133.4.384
25. Leirer VO, Yesavage JA, Morrow DG. Marijuana, aging, and task-difficulty effects on pilot performance. Aviat Space Environ Med 1989;60(12):1145-1152.
26. Yesavage JA, Leirer VO, Denari M, et al. Marijuana carry-over effects on aircraft pilot performance. Am J Psychiatry 1985;142(11):1325-1329. https://doi.org/10.1176/ajp.142.11.1325.
27. Yesavage JA, Leirer VO, Denari M, et al. Carry-over effects of marijuana intoxication on aircraft pilot performance: A preliminary report. Am J Psychiatry 1985;142(11):1325-1329. https://doi.org/10.1176/ ajp.142.11.1325
28. Robbe HWJ, O’Hanlon JF. Marijuana and actual driving performance: US Department of Transportation 1993. National Highway Traffic Safety Administration Final Report no. DOT- HS-808078. https://doi.org/10.21949/1525346
29. Berghaus G, Scheer N, Schmidt P, eds. Effects of cannabis on psychomotor skills and driving performance – a meta-analysis of experimental studies. In: Kloeden CN, McLean AJ, eds. Proceedings of the13th International Conference on Alcohol, Drugs and Traffic Safety, Vol. 1. Adelaide: NHMRC Road Accident Research Unit, 1995:403-409.
30. Ramaekers JG, Robbe HWJ, O’Hanlon JF. Marijuana, alcohol and actual driving performance. Hum Psychopharmacol 2000;15(7):551-558. https://doi.org/10.1002/1099-1077(200010)15:7<551::AID- HUP236>3.0.CO;2-P
31. Sexton BF, Tunbridge R, Brook-Carter N, et al. The influence of cannabis on driving. TRL report no. 477. Crowthorne: TRL Ltd, 2000. https://www.researchgate.net/publication/323309551_Sexton_BF_ Tunbridge_RJ_Brook-Carter_N_Jackson_PG_Wright_K_Stark_MM_and_K_Englehart_2001_The_ Influence_of_Cannabis_on_Driving_TRL_Project_Report_477 (accessed 1 August 2024).
32. Sexton BF, Tunbridge RJ, Board A, et al. The influence of cannabis and alcohol on driving. TRL report no. 543. Road Safety Division, Department of the Environment, Transport and the Regions, 2002. https://www.researchgate.net/publication/323309364_The_influence_of_cannabis_and_alcohol_on_ driving_Prepared_for_Road_Safety_Division_Department_for_Transport (accessed 1 August 2024).
33. Heishman SJ, Huestis MA, Henningfield JE, et al. Acute and residual effects of marihuana: Profiles of plasma THC levels, physiological, subjective and performance measures. Pharmacol Biochem Behav 1990;37(3):561-565. https://doi.org/10.1016/0091-3057(90)90028-g
34. Leirer VO, Yesavage JA, Morrow DG. Marijuana carry-over effects on aircraft pilot performance. Aviat Space Environ Med 1991;62(3):221-227.
35. Hitchcock LN, Tracy BL, Bryan AD, et.al., Acute effects of cannabis concentrate on motor control and speed: Smartphone-based mobile assessment. Front Psychiatr 2021;11:1-8. https://doi.org/10.3389/ fpsyt.2020.623672
36. Menetrey A, Augsburger M, Favrat B, et al. Assessment of driving capability through the use of clinical and psychomotor tests in relation to blood cannabinoids levels following oral administration of 20 mg dronabinol or of a cannabis decoction made with 20 or 60mg Delta 9-THC. J Analit Toxicol 2005;29(5):327-338. https://doi.org/10.1093/jat/29.5.327
37. Matheson J, Mann RE, Sproule B, et al. Acute and residual mood and cognitive performance of young adults following smoked cannabis. Pharmacology Biochemistry and Behavior 2020;194:1-8. https:// doi.org/10.1016/j.pbb.2020.172937
38. Pope HG, Gruber AJ, Hudson JI, et al. Neuropsychological performance in long-term cannabis users. Arch Gen Psychiatry 2001;58(10):909-915. https://doi.org/10.1001/archpsyc.58.10.909
39. Pope HG, Gruber AJ, Yurgeluntod D. The residual neuropsychological effects of cannabis – the current status of research. Drug Alcohol Depend 1995;38(1):25-34. https://doi.org/10.1016/0376-8716(95)01097-i
40. Bolla KI, Brown K, Eldreth D, et al. Dose-related neurocognitive effects of marijuana use. Neurology 2002;59(9):1337-1343. https://doi.org/.org/10.1212/01.wnl.0000031422.66442.49
41. Glodosky NA, Cuttler C, McLaughlin RJ. A review of the effects of acute and chronic cannabinoid exposure on the stress response. Front Neuroendocrinol 2021;63:100945. https://doi.org/10.1016/j. yfrne.2021.100945
42. Fletcher JM, Page JB, Francis DJ, et al. Cognitive correlates of long-term cannabis use in Costa Rican men. Arch Gen Psychiatry 1996;53(11):1051-1057. https://doi.org/10.1001/archpsyc.1996.01830110089011 43. Pope HG, Gruber AJ, Hudson JI, et al. Cognitive measures in long-term cannabis users. J Clin
Pharmacol 2002;42(11):S41-S47. https://doi.org/10.1001/archpsyc.58.10.909
44. Karoly HC, Milburn MA, Brooks-Russell A. Effects of high-potency cannabis on psychomotor performance in frequent cannabis users. Cannabis Cannabinoid Res 2022;7(1):107-115. https://doi.
org/10.1089/can.2020.0048
45. Karschner EL, Schwilke EW, Lowe RH, et al. Implications of plasma delta-9-tetrahydrocannabinol, 11-hydroxy-THC, and 11-nor 9-carboxy-THC concentrations in chronic cannabis smokers. J Analit Toxicol 2009;33(8):469-477. https://doi.org/10.1007/s00216-011-5331-6
46. Wadsworth EJK, Moss SC, Simpson SA, et al. Cannabis use, cognitive performance and mood in a sample of workers. J Psychopharmacol 2006;20(1):14-23. https://doi.org/10.1177/0269881105056644
47. Breitstadt R, Kauert G. Der Menschals Risiko und Sicherheitsreserve. Aachen: Shaker Verlag GmbH, 2004. 48. Blows S, Ivers RQ, Connor J, et al. Marijuana use and car crash injury. Addiction 2005;100(5):605-611.
https://doi.org/10.1111/j.1360-0443.2005.01100.x
49. Marsot A, Audebert C, Attolini L, et al. Population pharmacokinetics model of THC used by pulmonary route in occasional cannabis smokers. J Pharmacol Toxicol Method 2017;85(May-June):49-54. https:// doi.org/10.1016/j.vascn.2017.02.003
50. Johansson E, Agurell S, Hollister LE, et al. Prolonged apparent half-life of delta-1-tetrahydrocannabinol in plasma of chronic marijuana users. J Pharm Pharmacol 1988;40(5):374-375. https://doi. org/10.1111/j.2042-7158.1988.tb05272.x
51. Iribarne C, Berthou F, Baird S, et al. Involvement of cytochrome P450 3A4 enzyme in the N-demethylation of methadone in human liver microsomes. Chem Res Toxicol 1996;9(2):365-373. https://doi.org/10.1021/tx950116m
52. Matsunaga T, Iwawaki Y, Watanabe K, et al. Metabolism of delta-9 tetrahydrocannabinol by cytochrome P450 isozymes purified from hepatic microsomes of monkeys. Life Sci 1995;56(23- 24):2089-2095. https://doi.org/10.1016/0024-3205(95)00193-A
53. Hunt CA, Jones RT. Tolerance and disposition of tetrahydrocannabinol in man. J Pharmacol Exp Ther 1980;215(1):35-44. https://doi 10.1016/S0022-3565(25)32251-2 215:35;1980
54. Huestis MA, Henningfield JE, Cone EJ. Blood cannabinoids. I. Absorption of THC and formation of 11-OH THC and THCCOOH during and after smoking marijuana. J Analit Toxicol 1992;16(5):276- 282. https://doi.org/10.1093/jat/16.5.276
55. Huestis MA, Mitchell JM, Cone EJ. Urinary excretion profiles of 11-nor-9-carboxy-∆9- tetrahydrocannabinol in humans after single smoked doses of marijuana; J Anal Toxicol 1996;20(6):441-452. https://doi.org/10.1093/jat/20.6.441
56. Ellis GM, Mann MA, Judson BA, Schramm NT, et al. Excretion patterns of cannabinoid metabolites after last use in a group of chronic users. Clin Pharmacol Ther 1985;38(5):572-578. https://doi. org/10.1038/clpt.1985.226
57. Huestis MA, Mitchell JM, Cone EJ. Detection times of marijuana metabolites in urine by immunoassay and GC MS. J Anal Toxicol 1995;19(6):443-449. https://doi.org/10.1093/jat/19.6.443
58. Cairns ER, Howard RC, Hung CT, et al. Saliva THC levels and cannabis intoxication. Chemistry Division Report No 2411. Department of Scientific and Industrial Research. Lower Hutt, 1990. https:// doi.org/10.1007/BF02244217
59. Gross SJ, Worthy TE, Nerder L, et al. Detection of recent cannabis use by saliva delta-9-THC radioimmunoassay. J Anal Toxicol 1985;9(1):1-5. https://doi.org/10.1093/jat/9.1.1
60. Huestis MA, Cone EJ. Alternative testing matrices. In: Karch SB ed. Drug Abuse Handbook. Boca Raton: CRC Press, 2006:799; 1998. https://doi.org/10.1201/9781420048292.CH11
61. Huestis MA, Smith ML. Human cannabinoid pharmacokinetics and interpretation of cannabinoid concentrations in biological fluids and tissues. In: ElSohly MA, ed. Marijuana and the Cannabinoids. Forensic Science and Medicine. Humana Press, 2007. https://doi.org/10.1007/978-1-59259-947-9_9
62. Moskowitz H. Marijuana and driving. Accid Anal Prev 1985;17(4):323-345. https://doi. org/10.1016/0001-4575(85)90034-x
63. Perez-Reyes M, di Guiseppi S, Davis KH, Schindler VH, Cook CE. Comparison of effects of marijuana cigarettes of three different potencies. Clin Pharmacol Ther 1982;31:617-624. https://doi.org/10.1038/ clpt.1982.86
64. Perez-Reyes M, Owens SM, di Guiseppi S. The clinical pharmacology and dynamics of marijuana cigarette smoking. J Clin Pharmacol 1981;21(S1):2015-2075. https://doi.org/10.1002/j.1552-4604.1981. tb02596.x
65. South Africa. Cannabis for Private Purposes Act No. 7 of 2024.
66. South Africa. National Road Traffic Act No. 93 of 1996, section 65.
67. Jones AW, Morland JG, Liu RH. Driving under the influence of psychoactive substances: A historical
review. In: Jones AW, Mørland JG, Lui RH, eds. Alcohol, Drugs, and Impaired Driving: Forensic
Science and Law Enforcement Issues. CRC Press, 2020:32.
68. South Africa. Occupational Health and Safety Act No. 85 of 1993, sections 2(A), 2(C), 8, 9, 14, 23, of
the Regulations in terms of the Health and Safety Act.
69. National Union of Metalworkers of South Africa obo Kleinbooi v Umgeni Iron Works (Pty) Ltd (2012)
JOL 29594 (MEIBC).
70. Transport and Allied Workers Union of South Africa obo Dabula v Algoa Bus Company (2012)
11 BALR 1140 (SARPBC).
71. Cummins v New Denmark Colliery Anglo Thermal Coal (2015) JOL 33432 (CCMA).
72. Marasi v Petroleum Oil and Gas Corporation of South Africa (SOC) Ltd (2023) 10 BLLR 1043 (LC). 73. Constitution of the Republic of South Africa, 1996, section 36(1).
74. Ramaekers JG, Moeller MR, van Ruitenbeek P, et al. Cognition and motor control as a function of delta-9-THC concentration in serum and oral fluid: Limits of impairment. Drug Alcohol Dependence 2006;85(2):114-122. https://doi.org/10.1016/j.drugalcdep.2006.03.015
75. Substance Abuse and Mental Health Services Administration. https://www.samhsa.gov/ (accessed 17 November 2024).
76. European Workplace Drug Testing Society. European Guidelines for Workplace Drug Testing in Urine. https://www.ewdts.org/data/uploads/documents/2022-10-ewdts-guidelines-urine-final.pdf (accessed 17 November 2024).
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