- Email: [email protected]
LEAD IN PETROL: THE ALTERNATIVES
934
SIR,-The Basle school health service has
a
legal obligation
to
survey tuberculin reactions in schoolchildren. While small children are tested with ’Moro-patch’, the 14-year-olds are offered BCG vaccination after intracutaneous testing. In 1972 the tine test replaced the Mantoux test, mainly because some parents, who had rejected vaccination, had protested against their children having received an "injection" anyway. However, complications after BCG vaccination were noted in tine-negative children and Mantoux testing (with 10 IU PPD Berna) was again applied in children with negative reactions to the tine test whose parents had given their written consent to vaccination. In view of the poor results which Lunn and Johnson1 obtained in their studies with the tine test we did an analysis that confirmed their findings, with a sensitivity of 74% for the tine test.2 In a search for a better test we compared the tine test (Lederle Laboratories) with the Institut Merieux ’Mono-test’ (’Imotest’ in U.K.) in the school year 1980-81. Children and examiners were systematically allocated to the two tests, to get a balance of school types and examiners for each test. After a year we concluded that the mono_ test was no better than the tine test, but we realised that the two tests cannot be applied serially by the same person because the mono-test needs more pressure to penetrate the skin. Inadequate pressure when applying the mono-test might have been responsible for the low sensitivity of the imotest found by Dr Rudd and colleagues. EXPERIENCE OF TINE AND MONO TESTING, FOLLOWED BY MANTOUX WHERE INDICATED, IN BASLE SCHOOL HEALTH SERVICE
E PHENOTYPE DISTRIBUTION AND E ALLELE FREQUENCY IN NORMOLIPIDAEMIC AND TYPE V HYPERLIPIDAEMIC SUBJECTS
*No ofmdlviduals.
All had severe hypertriglyceridaemia (over 10 mmol/l) associated with fasting chylomicronaemia and increase of very low density lipoprotein (VLDL) triglycerides without evidence of post-
patients.
heparin lipoprotein lipase deficiency or apoC-II deficiency. Type III hyperlipoproteinaemia and causes of secondary hyperlipidaemia other than diabetes mellitus and obesity were excluded. Our method for isoelectric focusing of VLDL-apoproteins and other laboratory methods have been described previously.The distribution of apoE phenotypes in our forty-nine controls (table) accorded with previously reported population studies.2,3 None of our twenty type V patients had the homozygous E4 phenotype and eight had the heterozygous E4 phenotype (table). The apoE allele frequency was similar in the control group and in the type V patients. It seems unlikely that apoE4is a major determining factor in the expression of this disorder. Department of Internal Medicine, University of Nijmegen, 6500 HB Nijmegen, Netherlands
P. M. J. STUYT A. F. H. STALENHOEF P. N. M. DEMACKER A. VAN’T LAAR
LEAD IN PETROL: THE ALTERNATIVES *Sensitiv1ty=A +(A + B+C)x
100. For assumpuons
see text.
In the school year 1981-82 only the mono-test was used. Results can now be compared for large groups of children tested with tine and subsequent Mantoux and monotest and subsequent Mantoux, respectively. The table shows the resulting sensitivity, calculated under two assumptions-first, that the multipuncture tests do not produce false-positive results and, secondly, that iri the group not tested further (because of lack of parental consent) the same proportion of false-negative results would have been found as in those which were retested. Our data do not support the conclusion that the imotest is less reliable, but there seem to be fewer doubtful reactions with the mono-test than with tine test, which makes its use for screening
practicable. populations where tuberculosis is still present and where complications of vaccinations have to be avoided double testing still more
In
seems
indicated.
Institution of Social and Preventive Medicine,
University of Basle, 4052 Basle, Switzerland
URSULA ACKERMANN-LIEBRICH
HYPERLIPOPROTEINAEMIA TYPE V AND APOLIPOPROTEIN E4
SIR,-Dr Ghiselli and co-workers (Aug. 21, p. 405) reported a high frequency (74%) of the homozygous and heterozygous E4 apoE among type V hyperlipoproteinaemic patients. The allele frequency was 53% in contrast to 15% in normals. These workers concluded that apoE4 may predispose to a disturbance in the catabolism of triglyceride-rich lipoproteins. We have apoE phenotyped twenty type V hyperlipidaemic
phenotype
apoE4
1. Lunn JA,
Johnson AJ. Comparison of the tine and Mantoux tuberculin tests. Br Med J 1978; i: 1451-53. 2. Ackermann-Liebrich U, Ritzel G, Liebrich F. Erfahrungen mit dem Tuberkulin TineTest bei Reihenuntersuchungen. Schweiz Med Wschr 1980, 110: 329-31.
SjR,—Dr Grandjean and Dr Andersen (Aug. 7, p. 333) correctly concluded that lead is not an ideal petrol additive from an environmental point of view. In the same paragraph, however, they omitted mention of the major octane extender additive and instead listed alternatives to lead which cannot be used on a large scale, at least in the U.S.A., because of government prohibitions, technical
problems, or high costs. The manganese compound referred to was used commercially in the U.S. in unleaded gasoline for a short time, but its use is now the Environmental Protection Agency because it increases emissions of exhaust hydrocarbons. The other compounds listed, which are either alcohols or ethers, have been or are being used on a small scale, but all have drawbacks. Ethanol is very expensive: even with the current U.S.A. corn glut, its wholesale price is about$1.50 per gallon compared with$1.00 for gasoline (petrol), and it is used only where government subsidies make it economical. Methanol is a cheap relative to gasoline, but has undesirable effects on gasoline quality and is used in very limited volumes in the U.S.A Methanol can be made from coal, and some countries with large coal reserves are pushing methanol as an alternative fuel, but not as an octane extender. ter-butyl ether and ter-butyl alcohol are more expensive than gasoline and have some poor quality features that prevent their use at high concentrations, but are used where local economics favour them. They are produced mainly as byproducts in chemicals manufacture and augment other refinery processing for octane improvement, but do not eliminate them.
prohibited by
1. Stalenhoef AF, Casparie AF, Demacker PN, Stouten JT, Lutterman JA, van ’t LaarA Combined deficiency of apolipoprotein C-II and lipoprotein lipase m familial hyperchylomicronemia. Metabolism 1981, 30: 919-26. 2. Utermann G, Langenbeck U, Beisiegel U, Weber W. Genetics of the apolipoprotein E system in man. Am J Hum Genet 1980; 32: 339-47. 3. Zannis VI, Breslow JL. Human very low density lipoprotein apolipoprotein E isoprotein polymorphism is explained by genetic variation and posttranslational modification. Biochemistry 1980; 20: 1033-41.
935
Grandjean and Andersen did not mention catalytic reforming, which is the major method of octane improvement used by all large refineries. This improvement is more expensive than lead, and the process stream, called "reformate", consists mostly of aromatic hydrocarbons, some of which have known health hazard potentials. In summary, lead is not an ideal petrol additive, but neither are the alternatives.
_
P. F. D. VAN PEENEN T. O. WAGNER
Standard Oil Co. (Indiana), Chicago, Illinois 60601, U.S A.
HAIR ANALYSIS AND SELENIUM SHAMPOOS
SIR,-Mr Laker (July 31, p. 260) discusses the advantages of using hair as a biopsy tissue to assess trace mineral status. He mentions flameless atomic absorption spectrophometry, neutron activation analysis, and electron microprobe analysis, but inductively coupled plasma emission spectroscopy can also be used in multi-element analysis ofhair.1 doctors making use of hair mineral analysis should remember that, besides the influences of bleaching and tinting on trace mineral levels in hair, cold waving ("perming") reduces zinc and increases copper levels in hair.2When untreated samples are used hair mineral analysis can be a clinically useful method of screening for the status of many trace minerals.3 The caveats and usefulness of the clinical application of this technique have been summarised by the Hair Analysis Standardisation Board.4 To add to knowledge of hair treatments that affect the trace element content of hair, I would like to present evidence for hair selenium levels being increased by the use of selenium-containing
shampoos. A retrospective analysis of the results of trace element analysis of 171 hair samples of patients seen in a general medical private practice was undertaken, irrespective of clinical diagnosis. These hair samples had been analysed by inductively coupled argon plasma emission spectroscopy for twenty-one elements, including selenium, by Mineralab Inc., California. 1 g of hair was taken as close to the scalp as possible from the nape and measured no more than 5 cm. The samples were washed once in saturated free acid EDTA and then washed three times in de-ionised water, followed by 1 digestion in 70% nitric acid. 7 results were discounted because the hair had been dyed, bleached, or permed during the three months before the samples were taken. Of the remaining 164, 156 had hair selenium in the range 0 -. 2-60parts per million (ppm) and 7 had concentrations in the range 18-160 ppm (table). The high hair selenium group (18-160 ppm) 7 patients gave a history of using a shampoo (’Selsun’) which contains 2’ 5% w/v Quantitative element analysis by plasma emission spectroscopy. Science 1978; 202: 183-91. 2. McKenzie J. Alteration of zinc and copper concentration of hair. Am JClin Nutr 1978; 1. Fassel VA.
31: 470. 3. Bland J. Diagnostic usefulness of trace elements in human hair.
Department of Biochemistry, University of Puget Sound, Tacoma, Washington 98416, U.S.A.,
selenium sulphide in the three months before sampling. Patient VI (mild long-standing ulcerative colitis) did not use the shampoo on her own hair but had been using it twice a week for several months in washing the hair of her mentally handicapped child. It is reasonable to assume that she was absorbing the selenium through her skin. Patient VII had a high hair selenium with no history of selenium exposure. He had alcoholic cirrhosis. Aaseth et awl. noted a much decreased serum selenium in alcoholic cirrhotics and postulated increased urinary or faecal loss of this element. Hair, too, is an "excretory organ", and this may explain the abnormal value seen in patient VII. Little is known about the clinical significance of hair selenium, the most interesting work being evidence from China of low hair selenium levels in children with cardiomyopathy ("Keshan
disease"). 6,7 9 Portland
for elemental concentrations. P.O. Box 1982.
44, Trout Dale, Virginia, 24378, U.S.A.,
ELEVATED HAIR SELENIUM IN
7 SUBJECTS
T. STEPHEN DAVIES
MELANOMA, FLUORESCENT LIGHTS, AND POLYCHLORINATED BIPHENYLS
SIR,-Dr Beral and colleagues (Aug. 7, p. 290) have suggested a link between exposure to fluorescent lighting, office work, and an excess of malignant melanoma. Beral et al. stated that no other related causal factor known to be associated with melanoma could account for their observation. May I propose a causal factor which could be important? Polychlorinated biphenyls (PCBs) have been associated with melanoma and other cancers in man.8,9 PCBs are mainly used as a dielectric fluid in "closed" electric components, such as the small capacitors used in fluorescent light installations and other electric apparatus in offices such as air conditioners. In a recent investigation from Norway increased PCB concentrations (56-81 ng/m3) were detected in the office atmosphere and close to data screen terminals. 10 The concentration of PCBs was 50-80 times higher than outdoor concentrations. In the United States higher PCB levels have been found indoors than
outdoors.11,12z Especially high PCB levels J..Ig/m3), offices (0-10 J..Ig/m3),
detected in kitchens (0-31 and laboratories (0 - 21 J..Ig/m3). Outdoor concentrations were between 0 - 004 and 002 J..Ig/m3. Ona day with burnout of a fluorescent light ballast, the PCB levels were found to be over 50 times higher than normal (11-66 J..Ig/m3 vs 0’ 2 pg/m3) for that room, and levels remained high for 3-4 months. The fact that fluorescent lighting fixtures in offices emit PCB was reported in 1974.13 These investigations show that PCB may escape from "closed" electric systems, especially if the temperature is high. Indoor PCB exposure seems therefore to be of much greater importance than previously recognised, and may be linked to malignant melanoma. were
Danish National Institute
1981. 4. Hair Analysis Standardisation Board. Standardisation and interpretation of human hair
Road,
East Grinstead, West Sussex RH 19 4EB
of Occupational Health, ALLAN ASTRUP
DK-2900 Hellerup, Denmark
JENSEN
5.
Aaseth J, Thomassen Y, Real C, Alexander J, Norheim G. Decreased serum selenium in alcoholic cirrhosis. N Engl J Med 1980; 303: 944-45. 6. Keshan Disease Research Group of the Chinese Academy of Medical Sciences, Beijung. Epidemiologic studies on the etiologic relationships of selenium and Keshan disease. Chin MedJ 1979; 92: 477-82. 7. Editorial. Selenium in the heart of China. Lancet 1979; ii; 889-90. 8. Finklea IF. Important developments regarding PCBs. Am Ind Hyg Assoc J 1976; 37: 17-18 9. IARC Monographs on the evaluation of the carcinogenic risk of chemicals to humans, vol XVIII: Polychlorinated biphenyls and polybrominated biphenyls. Lyon: International Agency for Research on Cancer, 1978. 10. Digernes V, Astrup EG. Are datascreen terminals a source of increased PCBconcentrations in the working atmosphere? Int Arch Occup Envir Health 1982; 49: 193-97 11. MacLeod KE Sources of emissions of polychlorinated biphenyls into the ambient atmosphere and indoor air U.S. Environmental Protection Agency, Health Effects Research Laboratory, Research Triangle Park, North Carolina, 1979
(EPA-600/4-78-022). Polychlorinated biphenyls
12. MacLeod KE.
in
indoor air Envir Sci Technol 1981; 15:
926-28. 13.
Staiff DC, Quinby GE, Spencer DL, Starr HC. Bull Envir Contam 455-63
Toxicol
1974;
12:
SIR,-The Basle school health service has
a
legal obligation
to
survey tuberculin reactions in schoolchildren. While small children are tested with ’Moro-patch’, the 14-year-olds are offered BCG vaccination after intracutaneous testing. In 1972 the tine test replaced the Mantoux test, mainly because some parents, who had rejected vaccination, had protested against their children having received an "injection" anyway. However, complications after BCG vaccination were noted in tine-negative children and Mantoux testing (with 10 IU PPD Berna) was again applied in children with negative reactions to the tine test whose parents had given their written consent to vaccination. In view of the poor results which Lunn and Johnson1 obtained in their studies with the tine test we did an analysis that confirmed their findings, with a sensitivity of 74% for the tine test.2 In a search for a better test we compared the tine test (Lederle Laboratories) with the Institut Merieux ’Mono-test’ (’Imotest’ in U.K.) in the school year 1980-81. Children and examiners were systematically allocated to the two tests, to get a balance of school types and examiners for each test. After a year we concluded that the mono_ test was no better than the tine test, but we realised that the two tests cannot be applied serially by the same person because the mono-test needs more pressure to penetrate the skin. Inadequate pressure when applying the mono-test might have been responsible for the low sensitivity of the imotest found by Dr Rudd and colleagues. EXPERIENCE OF TINE AND MONO TESTING, FOLLOWED BY MANTOUX WHERE INDICATED, IN BASLE SCHOOL HEALTH SERVICE
E PHENOTYPE DISTRIBUTION AND E ALLELE FREQUENCY IN NORMOLIPIDAEMIC AND TYPE V HYPERLIPIDAEMIC SUBJECTS
*No ofmdlviduals.
All had severe hypertriglyceridaemia (over 10 mmol/l) associated with fasting chylomicronaemia and increase of very low density lipoprotein (VLDL) triglycerides without evidence of post-
patients.
heparin lipoprotein lipase deficiency or apoC-II deficiency. Type III hyperlipoproteinaemia and causes of secondary hyperlipidaemia other than diabetes mellitus and obesity were excluded. Our method for isoelectric focusing of VLDL-apoproteins and other laboratory methods have been described previously.The distribution of apoE phenotypes in our forty-nine controls (table) accorded with previously reported population studies.2,3 None of our twenty type V patients had the homozygous E4 phenotype and eight had the heterozygous E4 phenotype (table). The apoE allele frequency was similar in the control group and in the type V patients. It seems unlikely that apoE4is a major determining factor in the expression of this disorder. Department of Internal Medicine, University of Nijmegen, 6500 HB Nijmegen, Netherlands
P. M. J. STUYT A. F. H. STALENHOEF P. N. M. DEMACKER A. VAN’T LAAR
LEAD IN PETROL: THE ALTERNATIVES *Sensitiv1ty=A +(A + B+C)x
100. For assumpuons
see text.
In the school year 1981-82 only the mono-test was used. Results can now be compared for large groups of children tested with tine and subsequent Mantoux and monotest and subsequent Mantoux, respectively. The table shows the resulting sensitivity, calculated under two assumptions-first, that the multipuncture tests do not produce false-positive results and, secondly, that iri the group not tested further (because of lack of parental consent) the same proportion of false-negative results would have been found as in those which were retested. Our data do not support the conclusion that the imotest is less reliable, but there seem to be fewer doubtful reactions with the mono-test than with tine test, which makes its use for screening
practicable. populations where tuberculosis is still present and where complications of vaccinations have to be avoided double testing still more
In
seems
indicated.
Institution of Social and Preventive Medicine,
University of Basle, 4052 Basle, Switzerland
URSULA ACKERMANN-LIEBRICH
HYPERLIPOPROTEINAEMIA TYPE V AND APOLIPOPROTEIN E4
SIR,-Dr Ghiselli and co-workers (Aug. 21, p. 405) reported a high frequency (74%) of the homozygous and heterozygous E4 apoE among type V hyperlipoproteinaemic patients. The allele frequency was 53% in contrast to 15% in normals. These workers concluded that apoE4 may predispose to a disturbance in the catabolism of triglyceride-rich lipoproteins. We have apoE phenotyped twenty type V hyperlipidaemic
phenotype
apoE4
1. Lunn JA,
Johnson AJ. Comparison of the tine and Mantoux tuberculin tests. Br Med J 1978; i: 1451-53. 2. Ackermann-Liebrich U, Ritzel G, Liebrich F. Erfahrungen mit dem Tuberkulin TineTest bei Reihenuntersuchungen. Schweiz Med Wschr 1980, 110: 329-31.
SjR,—Dr Grandjean and Dr Andersen (Aug. 7, p. 333) correctly concluded that lead is not an ideal petrol additive from an environmental point of view. In the same paragraph, however, they omitted mention of the major octane extender additive and instead listed alternatives to lead which cannot be used on a large scale, at least in the U.S.A., because of government prohibitions, technical
problems, or high costs. The manganese compound referred to was used commercially in the U.S. in unleaded gasoline for a short time, but its use is now the Environmental Protection Agency because it increases emissions of exhaust hydrocarbons. The other compounds listed, which are either alcohols or ethers, have been or are being used on a small scale, but all have drawbacks. Ethanol is very expensive: even with the current U.S.A. corn glut, its wholesale price is about$1.50 per gallon compared with$1.00 for gasoline (petrol), and it is used only where government subsidies make it economical. Methanol is a cheap relative to gasoline, but has undesirable effects on gasoline quality and is used in very limited volumes in the U.S.A Methanol can be made from coal, and some countries with large coal reserves are pushing methanol as an alternative fuel, but not as an octane extender. ter-butyl ether and ter-butyl alcohol are more expensive than gasoline and have some poor quality features that prevent their use at high concentrations, but are used where local economics favour them. They are produced mainly as byproducts in chemicals manufacture and augment other refinery processing for octane improvement, but do not eliminate them.
prohibited by
1. Stalenhoef AF, Casparie AF, Demacker PN, Stouten JT, Lutterman JA, van ’t LaarA Combined deficiency of apolipoprotein C-II and lipoprotein lipase m familial hyperchylomicronemia. Metabolism 1981, 30: 919-26. 2. Utermann G, Langenbeck U, Beisiegel U, Weber W. Genetics of the apolipoprotein E system in man. Am J Hum Genet 1980; 32: 339-47. 3. Zannis VI, Breslow JL. Human very low density lipoprotein apolipoprotein E isoprotein polymorphism is explained by genetic variation and posttranslational modification. Biochemistry 1980; 20: 1033-41.
935
Grandjean and Andersen did not mention catalytic reforming, which is the major method of octane improvement used by all large refineries. This improvement is more expensive than lead, and the process stream, called "reformate", consists mostly of aromatic hydrocarbons, some of which have known health hazard potentials. In summary, lead is not an ideal petrol additive, but neither are the alternatives.
_
P. F. D. VAN PEENEN T. O. WAGNER
Standard Oil Co. (Indiana), Chicago, Illinois 60601, U.S A.
HAIR ANALYSIS AND SELENIUM SHAMPOOS
SIR,-Mr Laker (July 31, p. 260) discusses the advantages of using hair as a biopsy tissue to assess trace mineral status. He mentions flameless atomic absorption spectrophometry, neutron activation analysis, and electron microprobe analysis, but inductively coupled plasma emission spectroscopy can also be used in multi-element analysis ofhair.1 doctors making use of hair mineral analysis should remember that, besides the influences of bleaching and tinting on trace mineral levels in hair, cold waving ("perming") reduces zinc and increases copper levels in hair.2When untreated samples are used hair mineral analysis can be a clinically useful method of screening for the status of many trace minerals.3 The caveats and usefulness of the clinical application of this technique have been summarised by the Hair Analysis Standardisation Board.4 To add to knowledge of hair treatments that affect the trace element content of hair, I would like to present evidence for hair selenium levels being increased by the use of selenium-containing
shampoos. A retrospective analysis of the results of trace element analysis of 171 hair samples of patients seen in a general medical private practice was undertaken, irrespective of clinical diagnosis. These hair samples had been analysed by inductively coupled argon plasma emission spectroscopy for twenty-one elements, including selenium, by Mineralab Inc., California. 1 g of hair was taken as close to the scalp as possible from the nape and measured no more than 5 cm. The samples were washed once in saturated free acid EDTA and then washed three times in de-ionised water, followed by 1 digestion in 70% nitric acid. 7 results were discounted because the hair had been dyed, bleached, or permed during the three months before the samples were taken. Of the remaining 164, 156 had hair selenium in the range 0 -. 2-60parts per million (ppm) and 7 had concentrations in the range 18-160 ppm (table). The high hair selenium group (18-160 ppm) 7 patients gave a history of using a shampoo (’Selsun’) which contains 2’ 5% w/v Quantitative element analysis by plasma emission spectroscopy. Science 1978; 202: 183-91. 2. McKenzie J. Alteration of zinc and copper concentration of hair. Am JClin Nutr 1978; 1. Fassel VA.
31: 470. 3. Bland J. Diagnostic usefulness of trace elements in human hair.
Department of Biochemistry, University of Puget Sound, Tacoma, Washington 98416, U.S.A.,
selenium sulphide in the three months before sampling. Patient VI (mild long-standing ulcerative colitis) did not use the shampoo on her own hair but had been using it twice a week for several months in washing the hair of her mentally handicapped child. It is reasonable to assume that she was absorbing the selenium through her skin. Patient VII had a high hair selenium with no history of selenium exposure. He had alcoholic cirrhosis. Aaseth et awl. noted a much decreased serum selenium in alcoholic cirrhotics and postulated increased urinary or faecal loss of this element. Hair, too, is an "excretory organ", and this may explain the abnormal value seen in patient VII. Little is known about the clinical significance of hair selenium, the most interesting work being evidence from China of low hair selenium levels in children with cardiomyopathy ("Keshan
disease"). 6,7 9 Portland
for elemental concentrations. P.O. Box 1982.
44, Trout Dale, Virginia, 24378, U.S.A.,
ELEVATED HAIR SELENIUM IN
7 SUBJECTS
T. STEPHEN DAVIES
MELANOMA, FLUORESCENT LIGHTS, AND POLYCHLORINATED BIPHENYLS
SIR,-Dr Beral and colleagues (Aug. 7, p. 290) have suggested a link between exposure to fluorescent lighting, office work, and an excess of malignant melanoma. Beral et al. stated that no other related causal factor known to be associated with melanoma could account for their observation. May I propose a causal factor which could be important? Polychlorinated biphenyls (PCBs) have been associated with melanoma and other cancers in man.8,9 PCBs are mainly used as a dielectric fluid in "closed" electric components, such as the small capacitors used in fluorescent light installations and other electric apparatus in offices such as air conditioners. In a recent investigation from Norway increased PCB concentrations (56-81 ng/m3) were detected in the office atmosphere and close to data screen terminals. 10 The concentration of PCBs was 50-80 times higher than outdoor concentrations. In the United States higher PCB levels have been found indoors than
outdoors.11,12z Especially high PCB levels J..Ig/m3), offices (0-10 J..Ig/m3),
detected in kitchens (0-31 and laboratories (0 - 21 J..Ig/m3). Outdoor concentrations were between 0 - 004 and 002 J..Ig/m3. Ona day with burnout of a fluorescent light ballast, the PCB levels were found to be over 50 times higher than normal (11-66 J..Ig/m3 vs 0’ 2 pg/m3) for that room, and levels remained high for 3-4 months. The fact that fluorescent lighting fixtures in offices emit PCB was reported in 1974.13 These investigations show that PCB may escape from "closed" electric systems, especially if the temperature is high. Indoor PCB exposure seems therefore to be of much greater importance than previously recognised, and may be linked to malignant melanoma. were
Danish National Institute
1981. 4. Hair Analysis Standardisation Board. Standardisation and interpretation of human hair
Road,
East Grinstead, West Sussex RH 19 4EB
of Occupational Health, ALLAN ASTRUP
DK-2900 Hellerup, Denmark
JENSEN
5.
Aaseth J, Thomassen Y, Real C, Alexander J, Norheim G. Decreased serum selenium in alcoholic cirrhosis. N Engl J Med 1980; 303: 944-45. 6. Keshan Disease Research Group of the Chinese Academy of Medical Sciences, Beijung. Epidemiologic studies on the etiologic relationships of selenium and Keshan disease. Chin MedJ 1979; 92: 477-82. 7. Editorial. Selenium in the heart of China. Lancet 1979; ii; 889-90. 8. Finklea IF. Important developments regarding PCBs. Am Ind Hyg Assoc J 1976; 37: 17-18 9. IARC Monographs on the evaluation of the carcinogenic risk of chemicals to humans, vol XVIII: Polychlorinated biphenyls and polybrominated biphenyls. Lyon: International Agency for Research on Cancer, 1978. 10. Digernes V, Astrup EG. Are datascreen terminals a source of increased PCBconcentrations in the working atmosphere? Int Arch Occup Envir Health 1982; 49: 193-97 11. MacLeod KE Sources of emissions of polychlorinated biphenyls into the ambient atmosphere and indoor air U.S. Environmental Protection Agency, Health Effects Research Laboratory, Research Triangle Park, North Carolina, 1979
(EPA-600/4-78-022). Polychlorinated biphenyls
12. MacLeod KE.
in
indoor air Envir Sci Technol 1981; 15:
926-28. 13.
Staiff DC, Quinby GE, Spencer DL, Starr HC. Bull Envir Contam 455-63
Toxicol
1974;
12: