Document 1QdV62X1p3yjeLe2Le0Lg1KGZ

? (COMMISSION OER e u r o p Ais c h e n g e me in s c h a f t e n COMMISSION d es c o mmu n a u t Es e u r o p Ee n n e s 10 UNITED STATES ENVIRONMENTAL pr o t ec t io n ag en c y INTERNATIONAL SYMPOSIUM Environmental health aspects of lead Die gesundheitlichen Aspekte der Umweltverschmutzung durch Blei Les probl&mes sanitaires pos6s par le plomb present dans renvironnement OCCURRENCE AMD DISTRIBUTION OP LEAP AHD OTHER METALS IN TWO AREAS OP UNUSUAL DISEASE INCIDENCE IN BRITAIR DAVIES I, Department of Geography University College of Wales ABEKYSTwira, g r eat br it au t Amsterdam, October 2-6, 1972 N40697 2 SUMMARY The occurrence of lead, zinc, copper and cadmium has been investigated in two historic metal mining areas of Britain, namely, Cardiganshire and the Tamar Valley. Cancer and other diseases appear unusually prevalent in both areas. Total and plant-available lead and other metals are enriched in soils of the mineralized zones and lead is also unusually high in unpolluted soils. Enhanced amounts of heavy metals are entering the food chain through vegetables and drinking water but the significance of this is uncertain. DUP050057875 INTRODUCTION Environmental factors may be relevant in the aetiologies of several diseases and* in Britain, maps of some of these diseases have revealed greater incidences in the north and vest which reflects a recurrent geographical distinction between ''upland" and ''lowland11 Britain. For example, stomach cancer and lesions of the central nervous system (10), anencephaly (11) and pernicious anaemia (13) have their greatest prevalence in parts of upland Britain. Upland Britain, broadly that part lying north and west of a line drawn from mouth to mouth of the rivers Tees and Exe, is characterised by old rocks, organic-rich acid soils, higher rainfall and lower temperature, soft drinking water, extensive historic lead mining with local pollution and a lower population density* Of these factors much attention has been paid to a possible causative role of toxic trace metals. Soils rich in lead have been associated with multiple sclerosis (5* 15) and lead leached from spoil heaps with high stomach cancer in Cardiganshire (9). Cancers, diseases of the central nervous system and congen ital malformations are more prevalent in the defunct metal mining district (Tamar Valley) of Cornwall/bevon (12) and in one village three parts with contrasting cancer experience had three different water supplies, the worst part being served by well water derived from mineralised strata (1). The occurrence and distribution of lead and other metals in Cardiganshire and the Tamar Valley have been investigated. The following review is partly based on previously published work (2, 3, 4, 6, 7). THE STUDY ABBAS North Cardiganshire and the Tamar Valley are probably representative of other old mining areas in upland Britain. Both are underlain by bard Lower Palaeozoic sediments. In the Tamar Valley there are many igneous intrusions and the area- is flanked by the granite bosses which form the high ground Dartmoor end Bodmin Moor. Altitudes in the Tamar Valley range from sea level to about 300 m, but in Cardiganshire to above 800 m. Soils are generally acid brown earths and gleys, which become peaty above 300 m, and land use is chiefly grassland and forestry, with soma horticulture in the Tamar Valley. Metal mining began before the Roman Occupation but vas most active between 1700 and 1900 A.D. Output in Cardiganshire was primarily lead, silver and, latterly, zinc and in the Tamar Valley, arsenic, copper and lead. Now, the only evidence of past industry is scattered, abandoned mine workings and spoil: both areas are popular for holidays and tourism. TOTAL TRACE METALS IN SOILS In both areas the major pollutants were lead and zinc, and copper was prominent in the Tamar Valley. Cadmium was also studied since it occurs as a 'guest1 element in the zinc ore sphalerite. To establish the normal soil range for each metal, samples (0-15 cm) were taken for analysis from soils aim-tier to those of the mineralised zone but definitely free from pollution. Trace metal contents in soil are best described in terms of a log normal distribution and 99.9# of a population is contained within 4 the range mean - 3 x standard deviation* Results based on this calculation are given in Table 1 and the data allow polluted soils to be identified; e.g. a lead content>106 p.p*m. suggests unusual enrichment, most probably* by contamination* The lead values are interesting* for the abundance in the lithosphere is 16 p*p*m* and between 10 and 20 p*p*m. is commonly regarded as an average for soil* In a recent survey in the U*S*A* the (geometric) mean lead content was reported as 16 p.p*m* whence the normal range was 4*120 p.p.m* (14) * let values for Welsh soils formed on Ordovician and Silurian sediments are consistently* higher and 40 p*p*m* Pb is typical* In contrast, the mean lead level for soils on Triassio sandstone near Birmingham was approximately 20 p*p*m* (8) * There are several sources of pollution in mineralised regions* Undisturbed soils overlying ore bodies become metal enriched ^exemplified in Table 2; by natural processes. Fall-out from smelters allows enrichment downwind* The environs of spoil heaps are often phytotoxic because of contamination by wind blown fines or by drainage water from the spoil and only tolerant species, such as strains of Agrostis tenuis^grow there* Pollutants are also dispersed over a wide area with no apparent deleterious effects* In the mineralised part of the Tamar Valley 34 apparently uncontaminated, fertile pastures were sampled: 14 contained anomalous levels of at least one of the four metals analysed (Table 3) and the mean metal values for these 14 fields were all higher than the normal means of Table 1* The River Ystwyth, in Cardiganshire, contains within its floodplain some of the best local land* Before 1876 the uncontrolled injection of mine effluent into the river resulted in the deposition of finely ground ore particles on to these fields during floods with consequent poisoning of crops and stock* But these fields are now apparently fertile and productive* Summary data for samples from 17 of these fields are given in Table 3 and the very high levels of lead should be noted* The data in Table 3 also illustrate how the nature of the regional mineralisation controls pollutant levels* Cardiganshire was primarily a producer of lead and zinc whereas the Tamar Valley produced much more copper; the mean Values for lead, zinc and copper reflect these differing emphases# For rural people a significant contact with the physical environment is through home-grown vegetables* Accordingly, 12 gardens in the Tamar Valley were sampled, including some outside the mineralized part* Summary data are presented in Table 3* Every sample was anomalous with respect to at least one metal and. it is suspected that traditional gardening practices, such as heavy use of animal manure oT application of coal ash or soot may contribute to this enhancement* PLANT AVAILABIE METALS IN SOIL Only a small fraction of the total metal in soil is available for absorption by plants* The content^favailable metals is custom arily estimated by extracting soil with one of a Variety of solutions. Often, these solutions are diluted acids and acetic acid (2*5, v:v) is commonly used* Available metals in all samples were estimated in this way and, in general, there was a direct, linear relationship between the total metal content and its availability to plants* This is exemplified by the data in Table 4 which are the results of computing the correlation coefficient between total and available metal values for the soil samples DUP050057877 5 including those of Table 3* In practice, up\ ike of aa element by a plant depends not only on the availability oi that, element but also on factors such as soil reaction, antagonism and synergism by other elements, plant Species and differential uptake during the growing cycle. Radish fRaohanua sativus) has been used as a convenient test crop to measure actual uptake and nine experimental plots were harvested from Tamar Valley gardens# The results (Table 5) generally confirm the evidence from acetic acid extraction of soil that availability is proportional to total lead content* They do not support the contention that lead is rendered largely unavailable in neutral and alkaline soils* Radish plots were also grown in north Cardiganshire gardens (2) and broadly similar results were obtained, the main difference being that the lead values were generally higher : the Cardiganshire mean was 64 p,p,m, Fb with range 28-161 p,p,m*, compared with the Tamar Valley (Table 5) mean of 38 p.p,m, Fb and range 14-74 p.p.nu Within a plant, although lead tends to accumulate mostly in the root the amount in t he leaf also rises as uptake increases# Radish was grown (2) on a control soil and a high lead soil (44 and 11,200 p,p,m. Fb, respectively) : the control radish contained 10 p. p*m* Fb (dry matter) in both the root and leaves whereas the other contained 499 p*j?#m, Fb in the root and 136 p.p.m* Pb in the leaves. Moreover, the very high lead content of the second soil emphasises the point that lead is not very phytotoxic and "Toxicity symptoms are no sure guide to the plant f s metal content and maximum acceptable lead concentration are exceeded in apparently healthy crop8,, (4) , TRACE METALS IN WATER Allen-Frice (l) indicted the quality of Tamar Valley water supplies in his study of cancer distribution but he published no analyses* Accordingly, a very limited survey was made of rural domestic water quality. One litre samples were collected during the middle part of the day after rejecting the first three litres from the tap : it was assumed this would Aviate the possibility of lead contamination by acidic water standing in lead pipes. Table 6 records the results. The data are too few to justify close argument but they do point to the need for further invest igations, Assuming plumbosolvency may be a problem in soft waters below pH 7,8 then about half the samples are suspect* The World Health Organisation has advisory standards for cadmium and lead in water and some national organisations advise even lower lead limits* Therefore, samples have been identified in Table 6 where 50% of W*H*0* European standard was reached : 5 samples are suspect* It is worth noting that the two suspect lead samples (506 and 518) correspond with samples 16 and 53 in Table 5, where high radish leads are recorded, and both water supplies were derived from wells. No standards are set for the other three metals but, when compared with reports in the literature for natural waters, some of these values are also high* CONCLUSIONS It is not claimed in this paper that lead and other heavy metals are involved in the cause of diseases such as cancer. There appears to be a geographical association between high rates of several diseases and some westerly parts of Britain but corre lation is not necessarily indicative of cause and effect. DUP050057878 6, There is an emerging appreciation that sens rural enviroxtnenbs in 'upland Britain' are richer in lead and other metals than similar parts of 'lowland Britain'. Apart from the question of mining pollution, uncontaminsted soils on Ordovician and Silurian sediments consistently yield teed values two to three times higher than Soils on younger rooks. The situation is compounded by the extent of historic lead mining and its associated pollutions there Is at least one defunct lead mine in every Welsh county* Lead and other pollutants have been dispersed throughout the mineralised regions without necessarily causing visible environ mental damage. The inference from the work on lead in soil, in vegetables and in tap water, is that relatively large amounts are entering the food chain and that rural inhabitants of these areas airs exposed to a greater 'lead insult' than similar populations ^elsewhere in Britain. But the significance of this is very 'uncertain; e.g. the dietary importance of locally produced food in rural areas is not known and populations are so small that the medical data need careful interpretation. Current work includes more detailed investigation of the extent and nature of heavy metal pollution and how metal uptake by plants may be influenced. DUP050057879 REFERENCES 7 1. ALLEN-PRICE, E.D. I960. Uneven distribution of cancer in vest Devon with particular reference to the diverse water supply. Lancet. No. 7136, 1235-8. 2. ALLPWAZ, B.J. 1969. The soilsAvegetation of areas affected by mining for non-ferrous metalliferous ores, with special reference to cadmium, copper, lead and zinc. Ph.D. Thesis: Walts. 3. ALLOWAZ, B.J. & DAVIES, B.E. 1971. Trace element content of soils affected by base metal mining in Wales. Geoderma. , 197-207. 4. ALLOUAI, B.J. & DAVIES, B.E. 1971. Heavy metal content of plants growing on soils contaminated by lead mining. J. Aerie. Sci. (Camb.). 76. 321- 323- 5. CAMPBELL, A.M.G., HERDAH, G., TATIOW, N.F.T., & WHITTIE, E.G. 1950. Lead in relation to disseminate! sclerosis. Brain.73. 52-71. 6. DAVIES, B.E. 1968. Anomalous levels of trace elements in Welsh soils. Welsh Soils Disc. Grp. Kept.. 2, 72-87. 7. DAVIES, B.E. 1971. Trace metal content of soils affected by base metal mining in the west of England. Oikos. 22. 366-372. . 8. DAVIES, B.E. & HQIMES, P.L. 1972. Lead contamination of roadside soil and grass in Birmingham, England, in relation to naturally occurring levels. J. Aerie. Sci. (Camb.L In press. 9. HOWE, G.M. I960. The geographical distribution of cancer mortality in Wales, 1947-53. Trans. Inst. Brit. Geoer.. No. 28, 199-214. 10. HOWE, G.M. 1963. National atlas of disease mortality in the United Kingdom. Thomas Nelson, London, 111 pp. 11. PENROSE, L.S. 1957. Genetios of aneneephaly. J. Mental Def. Res.. 1, 4-15. 12. RECORDS & STATISTICS UNIT. 1966. Some contrasts in morbidity distribution. J. Rov. Coll. G.P.. 11, 74-83. 13* SCOTT, E. I960. Prevalence of pernicious anaemia in threat Britain, 3. 80--84. 14. SHACKIETTB, H.T., HAMILTON, J.C., BOERNGEN, J.G. & BOWLES, J.M. 1971. Elemental composition of surficial materials in the conterminous Edited States. Geological Survey Professional Paper 574-D. U.S. Govt. Printing Office, Washington. 15. WARREN, H.V., DEUVAULT, R.E. & CROSS, C.H. 1967. Possible correlations between geology and some disease patterns. Annin. N.Y. Acad. Sci.f 136. 657-710. DUP050057880 8, METAL Pb Zn a b Ou Cd TQTAL METAL CONTENT : D.p.nu Dig fiQIL fegmstrAg Mean Range 40 131 61 18 1.5 15 - 106 69 - 250 22 - 172 4--61 0 - 3.3 Sample U& 29 17 12 29 29 a = Cardiganshire b ss Tamar Valley Table 1 * Normal levels of metals in soils of the study areas. Zinc values differed significantly in the two areas and are quoted StfamfceJjj. SAMPLE NO. 12 345 6 TOTAL LEAD (p.p.m. dry soil) 45 68 142 64 58 15 Table 2* Lead contents of soil along a 100 m transect across a lead ore vein near Mold, Flintshire. TOTAL METAL CONTENT (p.p.m. DR! SOIL) TAMAR VALIEI (14 pasture samples) B) Mean Range Zn Mean Range Cu Mean Range Cd Mean Range 122 35 - 310 136 20 - 258 82 9 - 193 2.0 1.1 - 4.5 (12 garden samples) 260 41 - 522 396 73 - 793 131 25 - 684 2.7 1.3 - 4.3 ISWTITH VALLE! samples m alluvium} TM 90 " 2900 455 95 - 610 30 17-42 2.5 1.2 - 4,0 Table 3. Metal contents of contaminated soils DUP050057881 METAL PUS (Total v Available in soil) Fb Zn Cu Cd 9 LINEAR CORRELATION COEFFICIENT (r) TAMAR VALIEY YSTWYTH VA*1SI ('46 pastures) (12 gardens) (17 pluvial soils) 0.717*** 0.542*** 0.774*** m 0.885*** 0.727** 0.810** 0.746** 0.867*** O.903*** *** 0-1% ) * 1.0J6 ) Statistical * 5.0% ) significance NS< 5.O3S ) Table 4 Relationships between total and available metal contents of soil. SAMP1B mu 8 10 14 15 16 17 21 53 63 sm 7.0 5.5 6.6 5.3 7.1 6.6 5.3 5.7 6.6 LEAD CONTENT (p.p.m.) Plant Ash ftrallaftle to gntt 40 14.8 32 2.3 32 18.3 19 6.0 74 8.7 29 5.0 14 1.0 51 14.1 55 22.3 Table 5 lead content of radish grown in Tamar Valley gardens. Soil reaction (pHa) was determined in 0.01 M CaClg. DUP050057882 10 METAL CONTENT AS ^g. T1 SAMPLE NO. pH Pb Zn Ou Cd Mo 501 502 503 504 505 506 507 508 509 511 512 516 518 522 523 524 DETECTION LIMIT 9.3 8.9 7.0 7.8 9.0 5.9 8.4 8.9 9.0 8.7 7.7 7.5 7,0 7.6 6.2 8.8 < < < < 25 2960* < i < < < < 55* < < < 20 232 20 8 6 5 53 5 3 5 5 11 300 16 < 16 2 2 23 8 4 4 5 190 7 7 5 10 125 5 265 3 < < 2 2 1.5 12* 0.5 9* 0.4 2 0.8 2 0.8 2 0.2 2 3.0 2 2,2 2 4.2 2 1.4 2 0,2 9* 0.6 3< 3 o,4 2 0.2 3 10,2 2 0.2 < below detection limit* * 50% of WHO European limit* DUP050057883