A study conducted by measuring the intraoral vapor levels over a 24-hour period in patients with at least nine amalgam restorations showed the average daily dose of inhaled mercury vapor was 1.7 μg (range from 0.4 to 4.4 μg), which is approximately only 1% of the threshold limit value of 300 to 500 μg/day established by the World Health Organization, based on a maximum allowable environmental level of 50 μg/day in the workplace.[20] The World Health Organization (WHO) notes that exposure can be