Mark Richardson PhD discusses his study Inhalation of Mercury-Contaminated Particulate Matter by Dentists: An Overlooked Occupational Risk
The Journal of Human and Ecological Risk Assessment
Richardson, G Mark 2003
Dentists are exposed to mercury (Hg) during the removal of amalgam fillings. Recent research on dentists and other occupational groups report neurological impairment at Hg exposure levels below the current occupational TLV® (25 µg/m3) and/or the occupational BEI® (35 µg&sol Hg/g creatinine in urine).
Surveys of Hg° in the general office air of dental offices fail to measure the high levels of Hg-laden respirable amalgam particulate matter sprayed into the dentist’s breathing zone during the removal of old amalgam fillings. This respirable particulate matter represents the vast majority of daily Hg exposure in practicing dentists.
Despite this, no research is available on the pharmacokinetic fate of inhaled particulate amalgam Hg in humans. What indirect data does exist demonstrates that absorption from the lung occurs but that fecal excretion may predominate. As a result, urine analysis for Hg may be ineffective as a means of occupational monitoring.
Various countries are moving to limit the use of amalgam as a dental restorative material in order to protect dental patients from Hg exposure. However, dentists’ occupational exposure should also be considered as a justification for reduced amalgam use.
When the exposures in this study are added up, one gets the following levels.
Vapour inhaled during 4 removals (approx 40 minutes total) = 0.067 mg
Vapour inhaled during rest of time in office = 0.05 mg/Hg
Mercury in the particulate inhaled during 4 removals = 38 mg.
Total = 38,117 ug Hg per day.
When we asked Mark Richardson…”would patients be equally exposed”, here was his response…
Not exactly. Although any given patient would have the same particulate exposure during a removal, and exposure to the same vapour concentration in the breathing zone during the removal, the patient would not be exposed to the particulate of 4 removals per day (average used in paper) nor would the patient be exposed to the Hg vapour in the office air throughout the remainder of the working day (as assumed for the dentist). Finally, the patient would not be exposed day in and day out to the particulate.
In very approximate terms, the patient having a single removal would be exposed to approx 1/4th of the average daily exposure estimated for a dentist. However, the patient exposure would be considered ‘acute’ (single ‘dose’ or very short term duration) rather than chronic. Therefore the determination of risk would be very different, and would be considered much less serious than an equivalent exposure that continues daily over years.