- Email: [email protected]
LEAD IN PETROL
1042
oliogosaccharides (P. J. Reilly, personal communication) which might serve as a substrate for 0-glucosidase. Hydrolysis of "R-CMC" by an almond-derived enzyme preparation can be explained by the presence of cellulases in the commercial enzyme preparations used. Tierno et al found four proteins in the Sigma enzyme preparation by SDS gel electrophoresis, but did not establish the absence of cellulases. We have subjected Sigma 0-glucosidase (G4511, as Tierno et al used) to SDS gel electrophoresis and found over twenty proteins (figure). Isoelectric focusing on polyacrylamide gel also revealed more than twenty protein bands. We have gone on to demonstrate cellulase activity as well as 0-glucosidase activity in preparations supplied by Sigma and P-L Biochemical, Inc. Readily detected amounts of glucose and reducing sugars were liberated when pure cellulose (’Avicel’) was treated with either enzyme preparation. Tierno et al found glucose as an end product of treatment of "R-CMC" with "(3-glucosidase" because the preparations they used were contaminated with cellulases. In contrast cellulases have not been found in microbes isolated from the vagina, thus calling into question the relevance of these
experiments. GROWTH OF S AUREUS IN VARIOUS MEDIA
*InItlal
moculum=2’ 3x 105 Saureuslml. Each tube contained
tenzyme = 10
mg
0,4
mlliquid.
0-glucosidase (P-L Biochemical).
Tierno et al use a change in viscosity as evidence of hydrolysis. This is valid for non-crosslinked carboxymethylcellulose, which forms a true colloidal suspension in water, but not for crosslinked carboxymethylcellulose whose fibres swell when wet, but do not dissolve. The amount of swelling is reduced as ionic concentration increases.6 A non-flowing dispersion of swollen fibres in fluid, with a gel-like appearance, results when sufficient "R-CMC" is added to water to absorb all of the water. A true gel is not formed; the fibres remain intact, though much enlarged. Fibre swelling can be reduced by adding ionic materials (eg, NaCl, menstrual fluid, or even enzyme preparations such as the ones Tierno and co-workers used) and water is released from them so that the fibre suspension becomes more fluid. This is not a change in viscosity nor is it evidence of hydrolysis-it is a simple physical change due to the desorption of water. as
macroscopically and microscopically Rely tampons that had been by menstruating women who were vaginally carrying SEFproducing strains of S aureus. We have found no evidence that the cross-linked methylcellulose (CLD) in these tampons had undergone any degradation. worn
Procter & Gamble Company, Miami Valley Laboratories, Cincinnati, Ohio 45247, USA
JERRY J. KIRKLAND JAMES S. WIDDER
LEAD IN PETROL
SIR,-In response to your editorial (April 23, p 912), I would like to
disassociate
myself from
the title under which my Guardian
letter8 appeared. This was entirely the responsibility of the editor and, whilst I have reservations about the interpretation of the recent neuropsychological data, I would be the first to acknowledge that the Government-sponsored research has been of the highest quality. There is, however, one aspect of this debate which does worry me and it is typified by the letter from Dr Elwood9 criticising the Turin isotopic lead experimentsHaving demonstrated that the study is not epidemiologically perfect, Elwood suggests that the results cannot be extrapolated in any general sense because the meteorological conditions in Turin are unrepresentative of the country as a whole. Whilst this may or may not be true, it does not alter the fact that this was the area chosen by the EEC for the survey and approved by the petrochemical industry. Had the study produced a result closer to Elwood’s expectationstIdoubt whether the same criticisms would have been voiced.
I, too, have reservations about this study but they are rather different from those expressed by Elwood. First, the experiment should have been continued for longer than two years since isotopic ratios were still falling at the end of the steady-state period. Second, the study was concerned mainly with adults. Only limited information is available on preschool children but in two of these subjects isotopic ratios fell to 1.1100 (this represents a change of over 40%, based on samples taken one year after the steady-state phase had been discontinued). Finally, the study provides no measure of the contribution of vehicle emissions from outside the test area. Since lead in food is generally regarded as an important pathway from petrol lead to human beings, the results of the isotope lead experiment will underestimate substantially the real contribution from lead in petrol to human lead intake.12
Only two countries have introduced lead-free petrol. In Tokyo, blood lead levels have fallen by 70% since 1967.13,14 In America,a fall in petrol lead of 55% was accompanied a fall in blood levels of 37% (in children the fall was over 40%). Whatever alternative explanations are produced to account for these changes they appear somewhat strained when set against the more obvious conclusion that petrol is the main source of lead in human beings.
by
Campaign
for Lead-free Air,
2 Northdown
R. RUSSELL JONES, Deputy chairman
Street,
London N1 9BG
Contrary to the contention of Tierno et al, glucose cannot suffice the sole nutrient for S aureus. Nitrogen is essential and there is
none
7.
in "R-CMC".
Bergdoll MS, Crass BA, Reiser RF, et al. An enterotoxin-like protein in Staphylococus aureus
strains from patients with toxic shock
syndrome. Ann Intern Med 1982, 96
We attempted to grow a toxic shock syndrome strain ofS aureus in various combinations of distilled water, 3-glucosidase from the same source (P-L Biochemical) as used by Tierno et al, "R-CMC" chips, and 05% glucose. Cell numbers, after 24 h of incubation at 37°C, are shown in the table. As expected, cell numbers fell when the solution contained enzyme and "R-CMC". Growth occurred only with brain heart infusion broth, the positive control. Thus, our results contradict the report of Tierno that S aureus can grow with distilled water plus enzyme plus "R-CMC".
(part 2)&mid ot; 969-71. 8. Russell Jones R. How Government-sponsored surveys have polluted the lead and intelligence issue. Guardian, April 14, 1983. 9. Elwood PC. Turin isotopic lead experiment. Lancet 1983; i. 869. 10. Fachetti LS, Geiss F. Isotopic lead experiment: status report July 1982 (EUR 8352 EN). Brussels: Commission of the European communities. 11. Elwood PC, Gallagher J, Toothill C. Lead in petrol. Br Med J 1982, 284: 1189 12. Russell Jones R, Stephens R. The contribution of lead in petrol to human lead intake In Rutter M, Russell Jones R, eds. Lead versus health, sources and effects of low level lead exposure. Chichester: John Wiley, 1983. 13. Goldwater LJ, Hoover AW. An international study of ’normal’ levels in blood and
The hypotheses of Tierno et al situation since, beside our in vitro
14.
6
are not
relevant
experiments, we
Grignon J, Scallan AM Effect of pH and neutral gels. J Appl Polymer Sci 1980, 25: 2829-43.
salts upon the
the real life have examined to
swelling of cellulose
urine.
Arch Environ Health 1967, 15: 60.
Friberg L, Vahter M. Assessment of exposure to lead and cadmium through biological monitoring. Results ofa UNEP/WHO global study. Environ Res 1983; 30: 95 15. Annest JL. Trends in the blood lead levels ofthe U.S population. The second national health and nutrition examination survey, (NHANES H, 1976-1980).In Rutter M. Russell Jones R, eds. Lead versus health, exposure Chichester: John Wiley, 1983.
sources
and effects of low level lead
oliogosaccharides (P. J. Reilly, personal communication) which might serve as a substrate for 0-glucosidase. Hydrolysis of "R-CMC" by an almond-derived enzyme preparation can be explained by the presence of cellulases in the commercial enzyme preparations used. Tierno et al found four proteins in the Sigma enzyme preparation by SDS gel electrophoresis, but did not establish the absence of cellulases. We have subjected Sigma 0-glucosidase (G4511, as Tierno et al used) to SDS gel electrophoresis and found over twenty proteins (figure). Isoelectric focusing on polyacrylamide gel also revealed more than twenty protein bands. We have gone on to demonstrate cellulase activity as well as 0-glucosidase activity in preparations supplied by Sigma and P-L Biochemical, Inc. Readily detected amounts of glucose and reducing sugars were liberated when pure cellulose (’Avicel’) was treated with either enzyme preparation. Tierno et al found glucose as an end product of treatment of "R-CMC" with "(3-glucosidase" because the preparations they used were contaminated with cellulases. In contrast cellulases have not been found in microbes isolated from the vagina, thus calling into question the relevance of these
experiments. GROWTH OF S AUREUS IN VARIOUS MEDIA
*InItlal
moculum=2’ 3x 105 Saureuslml. Each tube contained
tenzyme = 10
mg
0,4
mlliquid.
0-glucosidase (P-L Biochemical).
Tierno et al use a change in viscosity as evidence of hydrolysis. This is valid for non-crosslinked carboxymethylcellulose, which forms a true colloidal suspension in water, but not for crosslinked carboxymethylcellulose whose fibres swell when wet, but do not dissolve. The amount of swelling is reduced as ionic concentration increases.6 A non-flowing dispersion of swollen fibres in fluid, with a gel-like appearance, results when sufficient "R-CMC" is added to water to absorb all of the water. A true gel is not formed; the fibres remain intact, though much enlarged. Fibre swelling can be reduced by adding ionic materials (eg, NaCl, menstrual fluid, or even enzyme preparations such as the ones Tierno and co-workers used) and water is released from them so that the fibre suspension becomes more fluid. This is not a change in viscosity nor is it evidence of hydrolysis-it is a simple physical change due to the desorption of water. as
macroscopically and microscopically Rely tampons that had been by menstruating women who were vaginally carrying SEFproducing strains of S aureus. We have found no evidence that the cross-linked methylcellulose (CLD) in these tampons had undergone any degradation. worn
Procter & Gamble Company, Miami Valley Laboratories, Cincinnati, Ohio 45247, USA
JERRY J. KIRKLAND JAMES S. WIDDER
LEAD IN PETROL
SIR,-In response to your editorial (April 23, p 912), I would like to
disassociate
myself from
the title under which my Guardian
letter8 appeared. This was entirely the responsibility of the editor and, whilst I have reservations about the interpretation of the recent neuropsychological data, I would be the first to acknowledge that the Government-sponsored research has been of the highest quality. There is, however, one aspect of this debate which does worry me and it is typified by the letter from Dr Elwood9 criticising the Turin isotopic lead experimentsHaving demonstrated that the study is not epidemiologically perfect, Elwood suggests that the results cannot be extrapolated in any general sense because the meteorological conditions in Turin are unrepresentative of the country as a whole. Whilst this may or may not be true, it does not alter the fact that this was the area chosen by the EEC for the survey and approved by the petrochemical industry. Had the study produced a result closer to Elwood’s expectationstIdoubt whether the same criticisms would have been voiced.
I, too, have reservations about this study but they are rather different from those expressed by Elwood. First, the experiment should have been continued for longer than two years since isotopic ratios were still falling at the end of the steady-state period. Second, the study was concerned mainly with adults. Only limited information is available on preschool children but in two of these subjects isotopic ratios fell to 1.1100 (this represents a change of over 40%, based on samples taken one year after the steady-state phase had been discontinued). Finally, the study provides no measure of the contribution of vehicle emissions from outside the test area. Since lead in food is generally regarded as an important pathway from petrol lead to human beings, the results of the isotope lead experiment will underestimate substantially the real contribution from lead in petrol to human lead intake.12
Only two countries have introduced lead-free petrol. In Tokyo, blood lead levels have fallen by 70% since 1967.13,14 In America,a fall in petrol lead of 55% was accompanied a fall in blood levels of 37% (in children the fall was over 40%). Whatever alternative explanations are produced to account for these changes they appear somewhat strained when set against the more obvious conclusion that petrol is the main source of lead in human beings.
by
Campaign
for Lead-free Air,
2 Northdown
R. RUSSELL JONES, Deputy chairman
Street,
London N1 9BG
Contrary to the contention of Tierno et al, glucose cannot suffice the sole nutrient for S aureus. Nitrogen is essential and there is
none
7.
in "R-CMC".
Bergdoll MS, Crass BA, Reiser RF, et al. An enterotoxin-like protein in Staphylococus aureus
strains from patients with toxic shock
syndrome. Ann Intern Med 1982, 96
We attempted to grow a toxic shock syndrome strain ofS aureus in various combinations of distilled water, 3-glucosidase from the same source (P-L Biochemical) as used by Tierno et al, "R-CMC" chips, and 05% glucose. Cell numbers, after 24 h of incubation at 37°C, are shown in the table. As expected, cell numbers fell when the solution contained enzyme and "R-CMC". Growth occurred only with brain heart infusion broth, the positive control. Thus, our results contradict the report of Tierno that S aureus can grow with distilled water plus enzyme plus "R-CMC".
(part 2)&mid ot; 969-71. 8. Russell Jones R. How Government-sponsored surveys have polluted the lead and intelligence issue. Guardian, April 14, 1983. 9. Elwood PC. Turin isotopic lead experiment. Lancet 1983; i. 869. 10. Fachetti LS, Geiss F. Isotopic lead experiment: status report July 1982 (EUR 8352 EN). Brussels: Commission of the European communities. 11. Elwood PC, Gallagher J, Toothill C. Lead in petrol. Br Med J 1982, 284: 1189 12. Russell Jones R, Stephens R. The contribution of lead in petrol to human lead intake In Rutter M, Russell Jones R, eds. Lead versus health, sources and effects of low level lead exposure. Chichester: John Wiley, 1983. 13. Goldwater LJ, Hoover AW. An international study of ’normal’ levels in blood and
The hypotheses of Tierno et al situation since, beside our in vitro
14.
6
are not
relevant
experiments, we
Grignon J, Scallan AM Effect of pH and neutral gels. J Appl Polymer Sci 1980, 25: 2829-43.
salts upon the
the real life have examined to
swelling of cellulose
urine.
Arch Environ Health 1967, 15: 60.
Friberg L, Vahter M. Assessment of exposure to lead and cadmium through biological monitoring. Results ofa UNEP/WHO global study. Environ Res 1983; 30: 95 15. Annest JL. Trends in the blood lead levels ofthe U.S population. The second national health and nutrition examination survey, (NHANES H, 1976-1980).In Rutter M. Russell Jones R, eds. Lead versus health, exposure Chichester: John Wiley, 1983.
sources
and effects of low level lead