What hygiene precaution must be followed when working with mercury?

The correct answer involves a crucial safety measure when handling mercury, particularly in the context of dental materials like amalgam. Storing scrap amalgam under water is a preventative measure to inhibit the release of mercury vapor into the air, thereby protecting dental professionals and patients from potential exposure to harmful levels of mercury. This method effectively contains the mercury, minimizing the risks associated with inhalation or contamination, especially in a dental practice where multiple procedures are performed.

Storing scrap amalgam in an open container would pose significant risks, as mercury vapors could easily escape into the environment. Similarly, the option of using mercury immediately without storage disregards the need for proper handling and containment protocols that ensure safety. While disposing of it in hazardous waste is indeed essential and necessary regarding the management and final disposal of mercury, the storage method during daily operations plays a pivotal role in immediate workplace safety. Therefore, the recommended practice of keeping scrap amalgam under water aligns with established safety precautions in dental settings where mercury is handled.