Effect of occupational exposure to elemental mercury in the amalgam on thymulin hormone production among dental staff

Abstract

Occupational exposure of dental staff to elemental mercury vapor released from dental amalgam is an issue of concern because of the possible immunological and neurological adverse outcomes. Recently, studies have reported that inorganic mercury induces immunosuppression by decreasing the production of thymus gland hormone (thymulin). This study aimed at investigating mercury body burden in dental staff and the relation of this burden to the potential impact of mercury on thymus gland hormone level (thymulin). Besides, the work aimed at verifying mercury effect on nitric oxide synthetase as a possible mechanism of its immunotoxicity. The study population consisted of a group of dental staff (n = 39) [21 dentists and 18 nurses] and a matched control group (n = 42). Each individual was subjected to detailed occupational and medical history taking and to estimation of urinary mercury (U-Hg) and blood mercury (B-Hg) as indicators of mercury body burden and exposure, respectively. Measurement of total thymulin hormone blood level, and plasma level of nitrite and nitrate (indicators of nitric oxide) was also done. The study showed a significantly increased U-Hg and B-Hg levels in the dental staff compared to their controls. This elevation of mercury body burden was associated with significant reduction in thymulin hormone blood level and nitric oxide parameters. These results were more evident in the group of nurses compared to the dentists. In conclusion, our results show that dentists and dental nurses have significant exposure to mercury vapor and point to the negative impact of mercury on thymus gland functions and confirm the implication that the nitric oxide pathway is a possible mechanism for this impact. Moreover, the study raises attention to the importance of hygiene measures in reduction of exposure to mercury vapor released from dental amalgam.

Use of Mercury in Dental Silver Amalgam: An Occupational and Environmental Assessment

“…Likewise, group 3 possesses greater risks compared to group 2 and so on. This statistical significance of age parameter on mercury levels in individuals has been in consistence with previously reported findings [ 9 , 23 , 24 ] and in contrast to [ 25 – 27 ].…”

Impact of occupational exposure to elemental mercury on some antioxidative enzymes among dental staff

“…Mercury is well-known to be absorbed by the body following inhalation, with numerous occupational studies showing air levels to be correlated with internal doses estimated by urinary mercury excretion (Farahat et al, 2009;Heyer et al, 2008;Levy, 1995;Mortada et al, 2002). There is much controversy about the safety of dental amalgam as it has been demonstrated to pose occupational risks to dental practitioners and their assistants…”

Rethinking the Dental Amalgam Dilemma: An Integrated Toxicological Approach

“…It had been shown that inorganic mercury induces immunosuppression by decreasing the production of thymus gland hormone (thymulin) in young mice [64]. Recently, a study in human (dental staff workers, dentists, and nurses) showed a significant increases of mercury levels in urine and blood compared to nondental personnel, and a concomitant reduction of thymulin hormone and nitric oxide in blood [65]. This study confirms the findings in humans of those previously reported with laboratory animals.…”