## 4 Discussion  
This scoping review consisted of 39 articles related to the biological exposure monitoring of healthcare workers, mainly nurses, pharmacists, and pharmacy technicians, via urine sampling. Based on the review, it appears that biological exposure monitoring has some value as most of the studies, regardless of study design, reported at least one sample with detectable levels of hazardous drugs. In addition, several studies found that uptake was still possible despite the existence of control measures such as gloves and closed-system transfer devices. This is noteworthy as studies have concluded that such exposure has led to statistically significant increases in genotoxic health effects in healthcare workers who are in contact with hazardous drugs [6; 56]. Regarding how the studies were conducted, there was a lack of standardization with respect to several important sample collection criteria, including when urine samples were collected during the shift and how samples were collected. This bears mentioning as there is a great deal of variability between individuals with respect to absorption, distribution, metabolism, and excretion of the exposed chemical agent [57]. Furthermore, there are already existing differences in the chemical and physical properties of various drugs, the quantity of drugs handled, as well as compliance with personal protective equipment usage--all of which can influence individual exposure [56]. Given that: (a) 24-h urine samples are more reflective of daily exposure [58], (b) the majority of studies which collected 24-h urine samples had at least one positive result, and (c) CP, the most commonly evaluated hazardous drug, is essentially eliminated in 24 h [59], it might be most prudent that 24-h urine voids be collected for biological exposure monitoring purposes. Unfortunately, there are very few details as to how 24-h urine samples are to be collected, with the exception of [PERSON] et al. [45], who collected each void over a 24-h period. The voided samples were refrigerated in between, and, subsequently, all of the individuals' voids were collated after sample collection was completed. The differences in results within and between studies are also likely associated with the inconsistency of the analytical methods, the number of drugs examined, and the analytical limit of detection. CP, IF, AFBA, and platinum compounds were commonly examined in the studies included in this review; however, because the limit of detection varied between studies, some of the study participants may have actually had drug contamination, but the analytical method employed was not sensitive enough to detect the drug in the urine. This is especially true for those studies which did not employ LC-MS/MS--which is currently accepted as the gold standard for the analysis of urine samples [15; 60]. Furthermore, some studies only examined one drug, whereas others were able to simultaneously detect multiple drugs from one sample. The latter is noteworthy as simultaneous analysis allows for a more thorough and representative assessment of the uptake of an individual occupationally exposed to hazardous drugs [60]. In addition, examining both the parent compound as well as urinary metabolites might provide a more accurate understanding of uptake [43; 44]. Although it was not possible to compare exposure results between studies, the longitudinal studies included in this review did suggest that the proportion of positive urinary samples decreased over time. This may be correlated with the fact that hazardous drug contamination on hospital surfaces is also showing a downward trend over time [11; 61]. This is reassuring from a health and safety perspective; however, without an established occupational exposure limit, it is best to adhere to the precautionary principle of as low as reasonably practicable or ALARP [62].