Final answer:
The environmental risk observed by a dialysis technician on the treatment floor is the presence of about one ounce (30mL) of fluid on the floor as it can cause slips and potential contamination.
Step-by-step explanation:
Among the observations made by a dialysis technician on the treatment floor, the one that poses an environmental risk is About one ounce (30mL) of fluid on the floor. This is because any spill poses a potential risk for slips and falls, as well as being a possible source of contamination, depending on the nature of the fluid. In contrast, the presence of a patient's family member during initiation of treatment, charts lying on bedside tables, and the wheels of the hemodialysis machine being locked, do not inherently pose environmental risks.