- Email: [email protected]
Lead concentrations in bones from Roman York
Journal of Archaeological
Science 1975, 2,235-237
Lead Concentrations in Bones from Roman York A. Mackie, A. Townshend and H. A. Waldron Departments of Chemistry and Social Medicine, University of Birmingham
Introduction Lead was of great importance to the Roman economy. Commercially it was a source of silver, which was refined from the lead ores, and domestically it formed the raw material from which their water systems were fabricated and from which linings for bronze cooking pots were made. There can be no doubt that the Romans exposed themselves to the risk of ingesting considerable quantities of lead from their food and drink and it may be inferred from the surviving books of the ancient medical writers that lead poisoning was relatively common and at times assumed epidemic proportions (Waldron, 1973). Objective evidence concerning the degree to which the Romans absorbed lead is, however, scanty. Gilfillan (1965) reported that the results from tests used to measure the lead content of 40 bones were consistent with his hypothesis that chronic lead poisoning had brought about the downfall of the Roman empire, but he neglected to reveal the levels of lead which he had found. Grandjean (1973), on the other hand, found very low lead concentrations in 19 bones dating from the Roman period in Denmark. Bone is a suitable material to use in a study of lead absorption since 90% or more of lead which is taken into the body finds its way to the skeleton where it is bound in a relatively inert state. The lead concentration in the skeleton is thus an index of the total lead absorption and hence, of the degree to which the environment of a single individual, or a single population, has been contaminated. In this paper we present the findings obtained from the analysis of bones from the Romano-British cemetery at Trentholme Drive, York, which was used for inhumations until about AD 300-320 (Wenham, 1968). Materials and Methods Lead tends to be distributed unevenly throughout the skeleton so that comparisons should properly be made only between analyses performed on the same bone. Ribs are usually abundant in excavations and present a suitable source of material for chemical analysis. Small pieces of rib (c. 2-4 cm in length) were obtained from 77 inhumations and later classified for age and sex from the description of the skeletal remains published by Warwick (1968). Each sample for analysis was cleaned in running glass-distilled water and soil and other surface contaminants were removed using a stiff nylon brush. The samples were dried in an air oven at 110°C overnight (about 18 hours). They were weighed and digested 235
236
A. MACKIE,
A. TOWNSHEND
Table I. Lead concentration in rib samples from Roman
Mean Males Females Unknown Total
60.2 85.5 62.0 63.5
sex
AND
(p.p.m. York
H. A. WALDRON
dry weight)
Standard deviation
n
25.7 60.8
55 9 13 17
21.8 31.6
in a mixture of concentrated perchloric and nitric acids on a hot plate and were then diluted to 100 ml volume with glass-distilled water. The solutions of bone were analysed for lead by atomic absorption spectroscopy using an air-acetylene flame. The concentration of lead in the solutions was determined by reference to a standard calibration curve. From these values the concentration of lead in the original bone sample could be calculated in parts/million dry weight. Results The results of the lead analyses are shown in Table 1. The mean concentration for the females is considerably higher than the means for the two other groups but is weighted by two unusually high values, one of 170.7 p.p.m. and one of 205.1 p.p.m. both in 25 year-olds (inhumations IO and 71, respectively). These are two of the highest concentrations found. In the male series only two values were greater than 100 p.p.m. A value of 182.1 p.p.m. was found in an elderly subject (inhumation 173) and one of 100.9 was found in a man of 25-30 (inhumation 322). Statistical analysis, however, showed that the difference between the means of the three groups shown in Table 1 is not significant (F= 1.26, P>O.O5). Discussion A number of studies have been undertaken to determine lead concentrations in contemporary bones. The results, however, have varied widely and mean values for some of the larger series are shown in Table 2. The mean lead concentration of the bones from York is somewhat greater than the highest value shown in this Table but not by a great margin. This suggests that there may have been more lead in the environment of those persons whose bones were deposited in the Trentholme Drive cemetery but it would not Table 2. Lead concentrations
Authors Barry & Mossman (1970) Schroeder & Tipton (1968) Nusbaum ef al. (1965)
Mean (1) 7.8
(p.p.m.)
in contemporary
Approximate mean with respect to dry weight
rib samples
Ratio
(2)
1 :2*
n
9.8
1:1.25
65
(wet weight) ;:h)
28.5
1.65
:1
91
;:h)
41.8
1965 : 1
175
* The conversion factors are those of Bryce-Smith & Waldron (unpublished work).
LEAD IN BONES FROM ROMAN
YORK
237
have been sufficient to have produced endemic lead poisoning in the population. Of course, the bones have been exposed to one environment which those used in modern analyses have not, that is, the soil in which they were buried. Soil from the excavation was not available for analysis and so the possibility of contamination from the soil cannot be ruled out even though York is not in an area which is likely to have a high soil lead content. (The average soil lead concentration is approximately 15 p.p.m.) Nor is it clear what effect lead in the soil will have on bones buried in it. Grandjean (1973; Grandjean & Holma, 1973) suggested that the low values which he found in Roman bones might have been due to lead loss into the soil although he did note a correlation between soil lead and bone lead concentrations, stating that the relationship was far from simple. The lead concentration in a single specimen from a child buried in a stone coffin, when soil effects would presumably be minimal, was 45.1 p.p.m., that is, the same order of magnitude as those found in the bones recovered from the soil. Table 3. Lead concenfrations (p.p.m. dry weight) as a funcfion of age in rib samples from males af Roman York Age-group Mean cont. n
o-19 47.1 2
20-29 60.2 13
30-39 59.5 17
40+ 61.5 14
Most modern studies show that bone lead concentrations increase with age, but no such effect was noted in the present study (see Table 3). This is not altogether surprising because of the small number involved and the error which must invariably occur in assigning an age to the bone. A number of the specimens came from the skeletons of individuals whose age could not be determined and in others, the age was given as a range, for example, 25-30. In this case, the individual was assigned to the age group which included the age in the mid-point, in the instance cited, age-group 20-29. Acknowledgements We are most grateful to Professor Roger Warwick for allowing us access to the bones which are in his department at Guy’s Hospital. Dr R. Stephens had made many helpful suggestions throughout the course of the study and we wish to extend our thanks to him. We would also like to thank Mr J. M. C. Groves for his assistance with the analysis. References Barry, P. S. I. & Mossman, D. B. (1970). Lead concentrations in human tissue. British Journal of Industrial Medicine 27, 339-351. Gilfillan, S. C. (1965). Lead poisoning and the Fall of Rome. Journal of Occupational Medicine 7, 53-60. Grandjean, P. (1973). Bly i danskere. En historisk-toksikologisk unders0gelse. Copenhagen : University of Copenhagen. Grandjean, P. & Holma, B. (1973). A history of lead retention in the Danish population. Environmental
Physiology
and Biochemistry
3, 268-213.
Nusbaum, R. E., Butt, E. M., Gilmour, T. C. & DiDio, S. L. (1965). Relation of air pollution to trace metals in bone. Archives of Environmental Health 10, 227-232. Schroeder, H. A. & Tipton, I. H. (1968). The human body burden of lead. Archives of Environmental
Health 17, 965-978.
Waldron, H. A. (1973). Lead poisoning in the ancient world. Medical History 17, 392-399. Warwick, R. (1968). Catalogue of skeletal remains. In (Wenham, L. P., Ed.) The RomanoBritish Cemetery at Trentholme Drive, York. London: H.M.S.O., 129-144. Wenbam, L. P. Ed. (1968). The Romano-British Cemetery at Trentholme Drive, York. London: H.M.S.O.
Science 1975, 2,235-237
Lead Concentrations in Bones from Roman York A. Mackie, A. Townshend and H. A. Waldron Departments of Chemistry and Social Medicine, University of Birmingham
Introduction Lead was of great importance to the Roman economy. Commercially it was a source of silver, which was refined from the lead ores, and domestically it formed the raw material from which their water systems were fabricated and from which linings for bronze cooking pots were made. There can be no doubt that the Romans exposed themselves to the risk of ingesting considerable quantities of lead from their food and drink and it may be inferred from the surviving books of the ancient medical writers that lead poisoning was relatively common and at times assumed epidemic proportions (Waldron, 1973). Objective evidence concerning the degree to which the Romans absorbed lead is, however, scanty. Gilfillan (1965) reported that the results from tests used to measure the lead content of 40 bones were consistent with his hypothesis that chronic lead poisoning had brought about the downfall of the Roman empire, but he neglected to reveal the levels of lead which he had found. Grandjean (1973), on the other hand, found very low lead concentrations in 19 bones dating from the Roman period in Denmark. Bone is a suitable material to use in a study of lead absorption since 90% or more of lead which is taken into the body finds its way to the skeleton where it is bound in a relatively inert state. The lead concentration in the skeleton is thus an index of the total lead absorption and hence, of the degree to which the environment of a single individual, or a single population, has been contaminated. In this paper we present the findings obtained from the analysis of bones from the Romano-British cemetery at Trentholme Drive, York, which was used for inhumations until about AD 300-320 (Wenham, 1968). Materials and Methods Lead tends to be distributed unevenly throughout the skeleton so that comparisons should properly be made only between analyses performed on the same bone. Ribs are usually abundant in excavations and present a suitable source of material for chemical analysis. Small pieces of rib (c. 2-4 cm in length) were obtained from 77 inhumations and later classified for age and sex from the description of the skeletal remains published by Warwick (1968). Each sample for analysis was cleaned in running glass-distilled water and soil and other surface contaminants were removed using a stiff nylon brush. The samples were dried in an air oven at 110°C overnight (about 18 hours). They were weighed and digested 235
236
A. MACKIE,
A. TOWNSHEND
Table I. Lead concentration in rib samples from Roman
Mean Males Females Unknown Total
60.2 85.5 62.0 63.5
sex
AND
(p.p.m. York
H. A. WALDRON
dry weight)
Standard deviation
n
25.7 60.8
55 9 13 17
21.8 31.6
in a mixture of concentrated perchloric and nitric acids on a hot plate and were then diluted to 100 ml volume with glass-distilled water. The solutions of bone were analysed for lead by atomic absorption spectroscopy using an air-acetylene flame. The concentration of lead in the solutions was determined by reference to a standard calibration curve. From these values the concentration of lead in the original bone sample could be calculated in parts/million dry weight. Results The results of the lead analyses are shown in Table 1. The mean concentration for the females is considerably higher than the means for the two other groups but is weighted by two unusually high values, one of 170.7 p.p.m. and one of 205.1 p.p.m. both in 25 year-olds (inhumations IO and 71, respectively). These are two of the highest concentrations found. In the male series only two values were greater than 100 p.p.m. A value of 182.1 p.p.m. was found in an elderly subject (inhumation 173) and one of 100.9 was found in a man of 25-30 (inhumation 322). Statistical analysis, however, showed that the difference between the means of the three groups shown in Table 1 is not significant (F= 1.26, P>O.O5). Discussion A number of studies have been undertaken to determine lead concentrations in contemporary bones. The results, however, have varied widely and mean values for some of the larger series are shown in Table 2. The mean lead concentration of the bones from York is somewhat greater than the highest value shown in this Table but not by a great margin. This suggests that there may have been more lead in the environment of those persons whose bones were deposited in the Trentholme Drive cemetery but it would not Table 2. Lead concentrations
Authors Barry & Mossman (1970) Schroeder & Tipton (1968) Nusbaum ef al. (1965)
Mean (1) 7.8
(p.p.m.)
in contemporary
Approximate mean with respect to dry weight
rib samples
Ratio
(2)
1 :2*
n
9.8
1:1.25
65
(wet weight) ;:h)
28.5
1.65
:1
91
;:h)
41.8
1965 : 1
175
* The conversion factors are those of Bryce-Smith & Waldron (unpublished work).
LEAD IN BONES FROM ROMAN
YORK
237
have been sufficient to have produced endemic lead poisoning in the population. Of course, the bones have been exposed to one environment which those used in modern analyses have not, that is, the soil in which they were buried. Soil from the excavation was not available for analysis and so the possibility of contamination from the soil cannot be ruled out even though York is not in an area which is likely to have a high soil lead content. (The average soil lead concentration is approximately 15 p.p.m.) Nor is it clear what effect lead in the soil will have on bones buried in it. Grandjean (1973; Grandjean & Holma, 1973) suggested that the low values which he found in Roman bones might have been due to lead loss into the soil although he did note a correlation between soil lead and bone lead concentrations, stating that the relationship was far from simple. The lead concentration in a single specimen from a child buried in a stone coffin, when soil effects would presumably be minimal, was 45.1 p.p.m., that is, the same order of magnitude as those found in the bones recovered from the soil. Table 3. Lead concenfrations (p.p.m. dry weight) as a funcfion of age in rib samples from males af Roman York Age-group Mean cont. n
o-19 47.1 2
20-29 60.2 13
30-39 59.5 17
40+ 61.5 14
Most modern studies show that bone lead concentrations increase with age, but no such effect was noted in the present study (see Table 3). This is not altogether surprising because of the small number involved and the error which must invariably occur in assigning an age to the bone. A number of the specimens came from the skeletons of individuals whose age could not be determined and in others, the age was given as a range, for example, 25-30. In this case, the individual was assigned to the age group which included the age in the mid-point, in the instance cited, age-group 20-29. Acknowledgements We are most grateful to Professor Roger Warwick for allowing us access to the bones which are in his department at Guy’s Hospital. Dr R. Stephens had made many helpful suggestions throughout the course of the study and we wish to extend our thanks to him. We would also like to thank Mr J. M. C. Groves for his assistance with the analysis. References Barry, P. S. I. & Mossman, D. B. (1970). Lead concentrations in human tissue. British Journal of Industrial Medicine 27, 339-351. Gilfillan, S. C. (1965). Lead poisoning and the Fall of Rome. Journal of Occupational Medicine 7, 53-60. Grandjean, P. (1973). Bly i danskere. En historisk-toksikologisk unders0gelse. Copenhagen : University of Copenhagen. Grandjean, P. & Holma, B. (1973). A history of lead retention in the Danish population. Environmental
Physiology
and Biochemistry
3, 268-213.
Nusbaum, R. E., Butt, E. M., Gilmour, T. C. & DiDio, S. L. (1965). Relation of air pollution to trace metals in bone. Archives of Environmental Health 10, 227-232. Schroeder, H. A. & Tipton, I. H. (1968). The human body burden of lead. Archives of Environmental
Health 17, 965-978.
Waldron, H. A. (1973). Lead poisoning in the ancient world. Medical History 17, 392-399. Warwick, R. (1968). Catalogue of skeletal remains. In (Wenham, L. P., Ed.) The RomanoBritish Cemetery at Trentholme Drive, York. London: H.M.S.O., 129-144. Wenbam, L. P. Ed. (1968). The Romano-British Cemetery at Trentholme Drive, York. London: H.M.S.O.