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Blood serum mercury test report
A clinical blood serum mercury test of 111 dentists and auxiliaries revealed that more than 50% had above normal serum mercury levels. This study showed that there may be a mercury health hazard in some dental environments. Acute mercury poisoning may be corrected simply by removing the cause, but long-term chronic effects are not known. Frequent screening of offices and personnel is advised. Experience reported here indicates that large amounts of mercury vapor are emitted when an amalgam carrier is heated over a flame to dislodge particles, and also, that water-covered amalgam scrap releases mercury vapor.
Blood serum mercury test report
John Vandenberge, DDS Allan S. Moodie, DPH, MB Ralph E. Keller, Jr., Baltimore ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■
I
M uch has been written about mercury hazards in the dental office.1,2 Yet it seems many den tists and their staffs are underinformed on diag nosing excess systemic mercury, precautionary m easures, effective clean-up methods, and con tamination hazards.3 Mercury is absorbed through the lungs, skin, and gastrointestinal tract,4,5 and excreted through the skin, feces, and urine. Because of easy avail ability, urine specimens are often used for mer cury absorption studies.4 N ot everyone agrees on whether blood serum or urine testing for mer cury is most accurate, but both seem to be more reliable than saliva, head hair, or fingernail test ing. In September 1974 at the M aryland Dental Convention at Ocean City, Md, a blood serum mercury test was conducted on 111 dentists and auxiliaries, 87 men and 24 women. Intravenous blood samples were drawn from the antecubital fossa in the usual manner. Samples were centri fuged, and the serum was separated and labeled. Each participant completed a questionnaire that included questions about the conditions in his dental office.
Table 1 ■ P erce n ta g e d is trib u tio n o f p a rtic ip a n ts w ith
Test results T est data seemed to indicate that blood mercury levels continue to rise with the number of years
va rio u s b lo o d m e rcu ry levels (/ug%) by years o f e xp o sure . Blood mercury levels Yr of exposure
0-0.9
1-1.9
2-2.9
3+
%
No. in group
0-4 5-9 10-14 15-19 20-29 30+
47.6 48.0 47.1 46.7 31.6 21.4
47.6 48.0 35.3 33.3 31.6 42.9
4.8 0.0 11.7 13.3 26.3 28.6
0.0 4.0 5.9 6.7 10.5 7.1
100 100 100 100 100 100
21 25 17 15 19 14
No. in group
46
45
14
6
100
111
Table 2 ■ P erce n ta g e d is trib u tio n o f p a rtic ip a n ts w ith o r w ith o u t d ire c t c o n ta c t w ith m e ta llic m e rcu ry and va rio u s b lo o d m e rcu ry levels (ng%). Blood mercury levels Less than 1 ng Contact (81) None (25)
37 48
1-1.9
2-2.9
42 40
14.9 4.0
3+ 6.1 4.0
% 100 100
of exposure, with no peak level (Table 1). An arbitrary division of the participants into two groups—those with one to nine years and those with ten or more years of exposure to mercury vapor—showed a statistically significant differ ence in blood levels to the 95% level (Table 1). The average blood mercury levels were signifi cantly higher in participants who admitted having direct contact with mercury (Table 2). O f those who had direct contact with mercury, there appeared to be a higher level of blood mer cury in individuals who worked in areas with linoleum floor covering (Table 3). Analysis also JADA, V ol. 94, J u n e 1977 ■ 1155
Table 3 ■ Percentage distribution of participants with various blood mercury levels (Mg%) and type of floor covering in offices of those admitting mercury contact. Blood mercury levels Floor covering
Less than 1 mg
1-1.9
2-2.9
3+
%
47 34
44 41
6 17
3 8
100 100
Carpet Linoleum
showed that dentists in carpeted offices do more amalgam restorations per day than those in lino leum-covered offices. This trend was particu larly evident in those who had been in practice for at least five to ten years. Perhaps this group is more aware of safe handling procedures of mercury from courses in dental schools or the dental literature. From the study there seemed to be no corre lation between the number of mercury-amalgam restorations done daily and the blood mercury levels of dental office personnel (Table 4). Partic ipants’ awareness of recent mercury spills also did not appear to affect their blood mercury lev els (Table 5). Each participant was asked about the presence of tremor, irritability, forgetfulness, and other symptoms of mercury poisoning. Most said they had no symptoms; no correlation was found be tween blood mercury levels and those admitting symptoms (Table 6). Table 4 ■ Percentage distribution of participants with various blood mercury levels (/ig%) and number of amalgam restorations they performed daily. Blood mercury levels No. of amalgam restorations
Less than 1
1.0-1.9
2.0-2.9
3.0+
37.5 37.7 55.5
46.0 42.2 27.7
10.4 10.4 11.1
6.1 4.4 5.7
Up to 10 11-20 21-30
% 100 100 100
able 5 ■ Percentage distribution of participants with various blood iercury levels (/¿g%) and admitted awareness or nonawareness of ¡cent mercury spills in office. Blood mercury levels vareness Female Male Total inawareness Female Male Total
0-0.9
1-1.9
2-2.9
3+
Total*
%
4 8 12(32%)
6 12 18(47%)
0 6 6(16%)
1 1 2(5%)
11 27 38
29 71 100
8 27 35(48%)
6 20 26(36%)
1 7 8(11%)
0 4 4(5%)
15 58 73
21 79 100
hose aware of recent spills, hose unaware of recent spills,
38 (34%). 73 (66%).
able 6 ■ Percentage distribution of participants admitting symptoms : mercury poisoning and various blood mercury levels (ng%). Blood mercury levels Jmitting symptoms Dne admitted
Less than 1
1.0-1.9
2.0-2.9
3+
Total
%
35.9 41.6
48.7 34.7
7.7 13.9
5.1 5.5
39 72
100 100
1156 ■ JADA, Vol. 94, June 1977
Handwriting was graded from the question naire according to firmness or lack of firmness of strokes, as an indication of possible mercury toxicity. One hundred and three participants showed no handwriting abnormalities. One had a distinct handwriting tremor; he was a 63-yearold dentist, in practice for 39 years, who had a reading of 1.9 /xg%. Of the seven who had sus picious tremors, five had blood serum mercury readings of 3.5, 0.6, 1.4, 1.0, and 2.2 fig%. But suspicious handwriting tremors may not necessarily be associated with highest blood ser um mercury levels, and the older dentists may have developed high blood serum mercury levels early in their practice. This may have left irrever sible brain and central nervous system tissue mercury levels, which could cause the tremors. It appears that within the range of blood mer cury levels found—up to 3.6 with a single level at 7 fig%—and because age and mercury levels are closely related, it is difficult to separate high blood serum mercury level and effects of ad vanced age.
Discussion More than 50% of the test participants had above normal blood serum mercury levels. And over 50% of dental offices surveyed by the Division of Labor and Industry, State of Maryland, were found to have mercury vapor levels above the permissible level.* Therefore, it seems advisable for members of the dental profession who have contact with mercury to have an annual check. Recommendations for control of mercury ex posure in dental offices were drafted in 1971 by the mercury contamination subcommittee of the Maryland Dental Association.6 Despite the sub committee and the ADA recommendations, Keller has found that, in his experience, water does not retain mercury vapor emissions from amalgam scrap. Mercury vapor has been detect ed 30 minutes after amalgam scrap was covered with water. Further studies by Keller are under way to determine a satisfactory method to pre vent amalgam scrap mercury vapor emissions. According to Keller, a great amount of mercuric vapor is released when amalgam carriers are heated over a flame to dislodge clogged amalgam particles. Dentists and their auxiliaries are strongly advised against this practice. The re leased vapors of heated amalgam can be meas-
ured several rooms away soon after evaporation has started. In acute poisoning, the body usually eliminates excess mercury in a few months. Little is known about chronic exposure effects over many years, especially at low levels. Different tissues absorb and eliminate mercury at different rates. The brain absorbs mercury slowly and eliminates it very slowly.5 Some commercial products claim to decontam inate floor and wall surfaces of operating areas. One product is a vacuum apparatus that has special attachments for cleaning up mercury spills. (The Maryland Dental Association can provide further information.t) It takes only a tiny droplet of liquid mercury in a rug or a crack in the floor covering to con tinuously emit mercury vapors. It is not known how long a droplet of mercury continues to vol atilize; it may be many years. The frequency of office mercury vapor inspections should be de termined partially by the test results. Negative results may decrease the frequency of inspec tions. However, personnel turnover should in crease the frequency of inspections. In the office of one of the authors (J.V.), the staff showed significant decrease in blood serum mercury levels in a six-month period after the carpet in the operatories was replaced by sheet vinyl floor covering. One small droplet in the car pet was thought to be the main cause our blood serum levels measured 3.5, 5.0, and 6.5 yxg% (dentist and two dental assistants, respectively). After six months, with the rugs removed, the readings were all 1.0 fig%. Great care also should be taken in packaging liquid mercury. Our office (J.V.) once received a shipment in plastic vials with loose tops. The result was a trail of mercury droplets from the receptionist’s desk to the storage area, and plen ty of spillage in the wrapping of the vials. The dental supply company was alerted and its rep resentative said that they would check other mercury in stock and communicate this problem with the manufacturer.
Summary Test results of 111 blood serum mercury mea surements were discussed. Various aspects of mercury hazards, precautions, and prevention methods were reviewed and some safety recom mendations were suggested. Experience suggests that water-covered amal gam scrap still releases mercury vapor and that a great amount of mercury vapor is released when an amalgam carrier is heated over a flame.
This test was sponsored by the Maryland Department of Labor and Industry, Industrial Hygiene Section. Laboratory service was provided by United Medical Laboratories, Portland, Ore. I (J. V.) thank Mr. Harvey A. Epstein, commissioner of the Mary land Department of Labor and Industry, who sponsored the mer cury testing project financially and supplied his staff, and Mr. Ralph E. Keller, Jr. for his on-site office inspections and his con tributions in the area of mercury hazard research. I also thank Dr. Allan S. Moodie for his contribution and his support in the development of this project and this publication. Dr. Vandenberge is in private practice and is part-time clinical instructor, University of Maryland, School of Dentistry. His ad dress is 1073 Maiden Choice Lane, Baltimore, 21229. Dr. Moodie is director of technical services, and Mr. Keller is a safety training specialist, Maryland Occupational Safety and Health Program, Department of Licensing and Regulation, Division of Labor and Industry, Baltimore. *The instrument used for the mercury vapor measurements was a Mercu ry Vapor Sniffer, J. W. Model MV-2 of The Bacharach Instrument Co., 1830 York Rd, Tlmonium, Md 21093. tMaryland Dental Association, 6701 Elkridge Landing Rd, Linthicum, Md, 21090. 1. Council on Dental Materials and Devices. Mercury surveys in dental offices. JADA 89:900 Oct 1974. 2. Gronka, P.A., and others. Mercury vapor exposures in den tal offices. JADA 81:923 Oct 1970. 3. Buchwald, H. Exposure of dental workers to mercury. Divi sion of Industrial Health Services, Alberta Department of Health, Alberta, Canada, May 1971, pp 27, 38, 54. 4. Hefferren, J.J. Mercury surveys of the dental office: equip ment, methodology, and philosophy. JADA 89:902 Oct 1974. 5. U. S. Department of Health, Education and Welfare, Public Health Service, National Institute for Occupational Safety and Health. Occupational Exposure to Inorganic Mercury, 1973, pp 17, 46, 47, 38. 6. The mercury contamination sub-committee of the MSDA, draft of proposed recommendations for control of mercury expo sure in dental offices, Baltimore, August 17, 1971.
Vandenberge— Moodie— Keller: BLOOD SERUM MERCURY TEST ■ 1157
Blood serum mercury test report
John Vandenberge, DDS Allan S. Moodie, DPH, MB Ralph E. Keller, Jr., Baltimore ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■
I
M uch has been written about mercury hazards in the dental office.1,2 Yet it seems many den tists and their staffs are underinformed on diag nosing excess systemic mercury, precautionary m easures, effective clean-up methods, and con tamination hazards.3 Mercury is absorbed through the lungs, skin, and gastrointestinal tract,4,5 and excreted through the skin, feces, and urine. Because of easy avail ability, urine specimens are often used for mer cury absorption studies.4 N ot everyone agrees on whether blood serum or urine testing for mer cury is most accurate, but both seem to be more reliable than saliva, head hair, or fingernail test ing. In September 1974 at the M aryland Dental Convention at Ocean City, Md, a blood serum mercury test was conducted on 111 dentists and auxiliaries, 87 men and 24 women. Intravenous blood samples were drawn from the antecubital fossa in the usual manner. Samples were centri fuged, and the serum was separated and labeled. Each participant completed a questionnaire that included questions about the conditions in his dental office.
Table 1 ■ P erce n ta g e d is trib u tio n o f p a rtic ip a n ts w ith
Test results T est data seemed to indicate that blood mercury levels continue to rise with the number of years
va rio u s b lo o d m e rcu ry levels (/ug%) by years o f e xp o sure . Blood mercury levels Yr of exposure
0-0.9
1-1.9
2-2.9
3+
%
No. in group
0-4 5-9 10-14 15-19 20-29 30+
47.6 48.0 47.1 46.7 31.6 21.4
47.6 48.0 35.3 33.3 31.6 42.9
4.8 0.0 11.7 13.3 26.3 28.6
0.0 4.0 5.9 6.7 10.5 7.1
100 100 100 100 100 100
21 25 17 15 19 14
No. in group
46
45
14
6
100
111
Table 2 ■ P erce n ta g e d is trib u tio n o f p a rtic ip a n ts w ith o r w ith o u t d ire c t c o n ta c t w ith m e ta llic m e rcu ry and va rio u s b lo o d m e rcu ry levels (ng%). Blood mercury levels Less than 1 ng Contact (81) None (25)
37 48
1-1.9
2-2.9
42 40
14.9 4.0
3+ 6.1 4.0
% 100 100
of exposure, with no peak level (Table 1). An arbitrary division of the participants into two groups—those with one to nine years and those with ten or more years of exposure to mercury vapor—showed a statistically significant differ ence in blood levels to the 95% level (Table 1). The average blood mercury levels were signifi cantly higher in participants who admitted having direct contact with mercury (Table 2). O f those who had direct contact with mercury, there appeared to be a higher level of blood mer cury in individuals who worked in areas with linoleum floor covering (Table 3). Analysis also JADA, V ol. 94, J u n e 1977 ■ 1155
Table 3 ■ Percentage distribution of participants with various blood mercury levels (Mg%) and type of floor covering in offices of those admitting mercury contact. Blood mercury levels Floor covering
Less than 1 mg
1-1.9
2-2.9
3+
%
47 34
44 41
6 17
3 8
100 100
Carpet Linoleum
showed that dentists in carpeted offices do more amalgam restorations per day than those in lino leum-covered offices. This trend was particu larly evident in those who had been in practice for at least five to ten years. Perhaps this group is more aware of safe handling procedures of mercury from courses in dental schools or the dental literature. From the study there seemed to be no corre lation between the number of mercury-amalgam restorations done daily and the blood mercury levels of dental office personnel (Table 4). Partic ipants’ awareness of recent mercury spills also did not appear to affect their blood mercury lev els (Table 5). Each participant was asked about the presence of tremor, irritability, forgetfulness, and other symptoms of mercury poisoning. Most said they had no symptoms; no correlation was found be tween blood mercury levels and those admitting symptoms (Table 6). Table 4 ■ Percentage distribution of participants with various blood mercury levels (/ig%) and number of amalgam restorations they performed daily. Blood mercury levels No. of amalgam restorations
Less than 1
1.0-1.9
2.0-2.9
3.0+
37.5 37.7 55.5
46.0 42.2 27.7
10.4 10.4 11.1
6.1 4.4 5.7
Up to 10 11-20 21-30
% 100 100 100
able 5 ■ Percentage distribution of participants with various blood iercury levels (/¿g%) and admitted awareness or nonawareness of ¡cent mercury spills in office. Blood mercury levels vareness Female Male Total inawareness Female Male Total
0-0.9
1-1.9
2-2.9
3+
Total*
%
4 8 12(32%)
6 12 18(47%)
0 6 6(16%)
1 1 2(5%)
11 27 38
29 71 100
8 27 35(48%)
6 20 26(36%)
1 7 8(11%)
0 4 4(5%)
15 58 73
21 79 100
hose aware of recent spills, hose unaware of recent spills,
38 (34%). 73 (66%).
able 6 ■ Percentage distribution of participants admitting symptoms : mercury poisoning and various blood mercury levels (ng%). Blood mercury levels Jmitting symptoms Dne admitted
Less than 1
1.0-1.9
2.0-2.9
3+
Total
%
35.9 41.6
48.7 34.7
7.7 13.9
5.1 5.5
39 72
100 100
1156 ■ JADA, Vol. 94, June 1977
Handwriting was graded from the question naire according to firmness or lack of firmness of strokes, as an indication of possible mercury toxicity. One hundred and three participants showed no handwriting abnormalities. One had a distinct handwriting tremor; he was a 63-yearold dentist, in practice for 39 years, who had a reading of 1.9 /xg%. Of the seven who had sus picious tremors, five had blood serum mercury readings of 3.5, 0.6, 1.4, 1.0, and 2.2 fig%. But suspicious handwriting tremors may not necessarily be associated with highest blood ser um mercury levels, and the older dentists may have developed high blood serum mercury levels early in their practice. This may have left irrever sible brain and central nervous system tissue mercury levels, which could cause the tremors. It appears that within the range of blood mer cury levels found—up to 3.6 with a single level at 7 fig%—and because age and mercury levels are closely related, it is difficult to separate high blood serum mercury level and effects of ad vanced age.
Discussion More than 50% of the test participants had above normal blood serum mercury levels. And over 50% of dental offices surveyed by the Division of Labor and Industry, State of Maryland, were found to have mercury vapor levels above the permissible level.* Therefore, it seems advisable for members of the dental profession who have contact with mercury to have an annual check. Recommendations for control of mercury ex posure in dental offices were drafted in 1971 by the mercury contamination subcommittee of the Maryland Dental Association.6 Despite the sub committee and the ADA recommendations, Keller has found that, in his experience, water does not retain mercury vapor emissions from amalgam scrap. Mercury vapor has been detect ed 30 minutes after amalgam scrap was covered with water. Further studies by Keller are under way to determine a satisfactory method to pre vent amalgam scrap mercury vapor emissions. According to Keller, a great amount of mercuric vapor is released when amalgam carriers are heated over a flame to dislodge clogged amalgam particles. Dentists and their auxiliaries are strongly advised against this practice. The re leased vapors of heated amalgam can be meas-
ured several rooms away soon after evaporation has started. In acute poisoning, the body usually eliminates excess mercury in a few months. Little is known about chronic exposure effects over many years, especially at low levels. Different tissues absorb and eliminate mercury at different rates. The brain absorbs mercury slowly and eliminates it very slowly.5 Some commercial products claim to decontam inate floor and wall surfaces of operating areas. One product is a vacuum apparatus that has special attachments for cleaning up mercury spills. (The Maryland Dental Association can provide further information.t) It takes only a tiny droplet of liquid mercury in a rug or a crack in the floor covering to con tinuously emit mercury vapors. It is not known how long a droplet of mercury continues to vol atilize; it may be many years. The frequency of office mercury vapor inspections should be de termined partially by the test results. Negative results may decrease the frequency of inspec tions. However, personnel turnover should in crease the frequency of inspections. In the office of one of the authors (J.V.), the staff showed significant decrease in blood serum mercury levels in a six-month period after the carpet in the operatories was replaced by sheet vinyl floor covering. One small droplet in the car pet was thought to be the main cause our blood serum levels measured 3.5, 5.0, and 6.5 yxg% (dentist and two dental assistants, respectively). After six months, with the rugs removed, the readings were all 1.0 fig%. Great care also should be taken in packaging liquid mercury. Our office (J.V.) once received a shipment in plastic vials with loose tops. The result was a trail of mercury droplets from the receptionist’s desk to the storage area, and plen ty of spillage in the wrapping of the vials. The dental supply company was alerted and its rep resentative said that they would check other mercury in stock and communicate this problem with the manufacturer.
Summary Test results of 111 blood serum mercury mea surements were discussed. Various aspects of mercury hazards, precautions, and prevention methods were reviewed and some safety recom mendations were suggested. Experience suggests that water-covered amal gam scrap still releases mercury vapor and that a great amount of mercury vapor is released when an amalgam carrier is heated over a flame.
This test was sponsored by the Maryland Department of Labor and Industry, Industrial Hygiene Section. Laboratory service was provided by United Medical Laboratories, Portland, Ore. I (J. V.) thank Mr. Harvey A. Epstein, commissioner of the Mary land Department of Labor and Industry, who sponsored the mer cury testing project financially and supplied his staff, and Mr. Ralph E. Keller, Jr. for his on-site office inspections and his con tributions in the area of mercury hazard research. I also thank Dr. Allan S. Moodie for his contribution and his support in the development of this project and this publication. Dr. Vandenberge is in private practice and is part-time clinical instructor, University of Maryland, School of Dentistry. His ad dress is 1073 Maiden Choice Lane, Baltimore, 21229. Dr. Moodie is director of technical services, and Mr. Keller is a safety training specialist, Maryland Occupational Safety and Health Program, Department of Licensing and Regulation, Division of Labor and Industry, Baltimore. *The instrument used for the mercury vapor measurements was a Mercu ry Vapor Sniffer, J. W. Model MV-2 of The Bacharach Instrument Co., 1830 York Rd, Tlmonium, Md 21093. tMaryland Dental Association, 6701 Elkridge Landing Rd, Linthicum, Md, 21090. 1. Council on Dental Materials and Devices. Mercury surveys in dental offices. JADA 89:900 Oct 1974. 2. Gronka, P.A., and others. Mercury vapor exposures in den tal offices. JADA 81:923 Oct 1970. 3. Buchwald, H. Exposure of dental workers to mercury. Divi sion of Industrial Health Services, Alberta Department of Health, Alberta, Canada, May 1971, pp 27, 38, 54. 4. Hefferren, J.J. Mercury surveys of the dental office: equip ment, methodology, and philosophy. JADA 89:902 Oct 1974. 5. U. S. Department of Health, Education and Welfare, Public Health Service, National Institute for Occupational Safety and Health. Occupational Exposure to Inorganic Mercury, 1973, pp 17, 46, 47, 38. 6. The mercury contamination sub-committee of the MSDA, draft of proposed recommendations for control of mercury expo sure in dental offices, Baltimore, August 17, 1971.
Vandenberge— Moodie— Keller: BLOOD SERUM MERCURY TEST ■ 1157