- Email: [email protected]
Tail hair as an indicator of environmental exposure of cows to lead and cadmium in different industrial areas
ARTICLE IN PRESS
Ecotoxicology and Environmental Safety 66 (2007) 127–131 www.elsevier.com/locate/ecoenv
Tail hair as an indicator of environmental exposure of cows to lead and cadmium in different industrial areas R.C. Patraa,, D. Swarupa, Ram Nareshb, Puneet Kumara, D. Nandia, Pallav Shekhara, S. Royc, S.L. Alic a
Environmental Medicine Laboratory, Division of Medicine, Indian Veterinary Research Institute, Izatnagar 243 122, UP, India b Division of Animal Health, IVRI Regional Center at Mukteswar, Nainital, Uttaranchal, India c Division of Clinical Medicine, College of Veterinary Science and Animal Husbandry, Anjora, Durg, Chattisgarh, India Received 22 May 2005; received in revised form 8 January 2006; accepted 22 January 2006 Available online 23 March 2006
Abstract This study examines the use of tail hair from cows as a possible biomarker of environmental exposure to lead and cadmium around different industrial areas. Respective blood and tail hair samples were collected from a total of 317 apparently healthy cows above 3 years of age. This includes 287 cows reared in industrial and urban areas and 30 cows from areas free from polluting sources. Significantly ðPo0:05Þ higher lead and cadmium residues were recorded in hair from cows reared around lead–zinc smelter and closed lead cum operational zinc smelter. However, cows from those areas had significantly ðPo0:05Þ higher blood lead but not cadmium concentration as compared to respective control value. Although mean blood lead concentration in cows around aluminum processing plant and urban cum small industrial areas and that of cadmium around steel processing plant were significantly ðPo0:05Þ higher than respective control, the mean hair lead and cadmium content remained statistically ðP40:05Þ comparable to that of respective control values. The blood lead was significantly correlated with hair lead ðr ¼ 0:672, Po0:01Þ and cadmium ðr ¼ 0:309, Po0:05Þ. There was a significant correlation between lead and cadmium concentration ðr ¼ 0:610, Po0:01Þ in hair and a nonsignificant correlation between blood and hair cadmium suggesting that cadmium accumulation in hair was influenced by blood and hair lead concentrations in cows environmentally exposed to lead. r 2006 Elsevier Inc. All rights reserved. Keywords: Lead; Cadmium; Tail hair; Cow; Blood
1. Introduction Environmental pollution due to toxic heavy metals has gained widespread attention due to its various deleterious health effects in man and other animals. Lead and cadmium are the two most abundant toxic metals in the environment with no detectable beneficial biological roles. The common sources of lead and cadmium are diverse in nature including natural and anthropogenic processes such as combustion of coal and mineral oil, smelters, mining, alloy processing units, paint industries, etc. (Dwivedi et al., 2001; Phillips et al., 2003; Patra et al., 2005; Swarup et al., Corresponding author. Fax: +91 581 2303284.
E-mail addresses: (R.C. Patra).
[email protected],
[email protected]
0147-6513/$ - see front matter r 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.ecoenv.2006.01.005
2005). These anthropogenic activities and vehicular emissions contribute to the entry of toxic metals to human’s and other animal’s food chains (Okada et al., 1997). Chronic exposure to these sulfhydryl reactive metals through various routes results in their higher accumulation in tissues, bones, hair and blood, and monitoring of these toxic metals in biological materials essentially indicates the status of environmental degradation (Quig, 1998; Phillips et al., 2003; Raab et al., 2002; Vahter and Marafante, 1983). Hair fiber is a metabolically dead material after it leaves the epidermis. However, the fiber in the root during its growth is metabolically very active. Higher arsenic level in wool fiber has been reported in sheep fed with a higharsenic diet as it is readily taken up by the cells of the root (Raab et al., 2002). This signifies the role of hair fiber in
ARTICLE IN PRESS R.C. Patra et al. / Ecotoxicology and Environmental Safety 66 (2007) 127–131
128
diagnosis of chronic exposure and past poisonings of certain metals. Hair samples have been used for noninvasive diagnosis of cadmium toxicity in humans (Struempler et al., 1985). The frequency of diseases such as autism has been predicted in humans using data on hair concentrations of cadmium and other minerals (Wecker et al., 1985). It is therefore hypothesized that the tail hair from cattle reared around industrial areas may serve as a tool for monitoring exposure to heavy metal pollutants such as lead and cadmium. 2. Material and methods 2.1. Animals Cows ðn ¼ 287Þ above 3 years of age, reared and allowed to graze on pasture within 2 km of industrial units, were used for this study. The industrial units in various parts of India included coal mining ðn ¼ 45Þ, rock phosphate mining cum phosphate fertilizer plant ðn ¼ 21Þ, steel processing unit ðn ¼ 46Þ, urban areas with small industrial units ðn ¼ 55Þ, aluminum processing plant ðn ¼ 25Þ, closed lead cum operational zinc smelter ðn ¼ 7Þ, and lead–zinc smelter ðn ¼ 88Þ. Samples were also collected from 30 cows of identical age which were reared in areas apparently free from industrial or urban polluting sources to serve as controls.
2.2. Sampling Surveys were carried out over a period of 3 years from 2002 to 2005. Respective blood and hair samples were collected from each animal with the consent of the animal’s owners. About 5 mL blood samples were collected by jugular venepuncture into nitric-acid-washed heparinized glass vials. Hair samples were collected from the tail switch using a scalpel and kept in separate plastic bags. Samples of soil and fodder, provided to the cows, were collected in polythene bags for further processing. The blood samples were stored at 4–8 1C. Soil, hair and fodder samples were stored at room temperature until wet digestion within a period of 1 week from collection of samples.
2.3. Analysis of lead and cadmium Hair samples were washed sequentially with acetone, distilled water, and acetone to remove adherent dirt and organic materials (IAEA, 1978) and fodder samples were washed by deionized water. Approximately, 1 g each of the hair sample after drying, 5 mL of blood, 5 g of fodder, and 1 g of soil sample were wet digested with nitric and perchloric acid mixture (3:1 v/v) at low heat (o90 1C). Two to three blank samples were run simultaneously with each batch of the digestion where biosample was substituted by deionized triple-distilled water. Lead and cadmium concentrations in digested samples were estimated after suitable dilution using an atomic absorption spectrophotometer (Electronic Corp. of India, Ltd.) at the wavelengths of 217 nm (detection limit, 0.025 mg/mL) and 229.5 nm (detection limit, 0.005 mg/mL), respectively, with 6-mA current and the values were expressed in mg/mL of blood and mg/g of hair, fodder, or soil (dry weight basis).
2.4. Analysis of data The data were analyzed using one-way analysis of variance to compare the mean values and are expressed as mean7SE throughout the text. The correlation between blood and hair concentrations of lead and cadmium were analyzed using standard statistical methods (Snedecor and Cochran, 1994).
3. Results Table 1 shows the lead and cadmium concentrations in blood and hair from cows ðn ¼ 317Þ reared in different industrial/urban and unpolluted areas. Cows in the vicinity of only lead–zinc smelter (15.0970.85 and 2.6270.32 mg/g) and closed lead cum operational zinc smelter (11.7274.02 and 5.7272.75 mg/g) had significantly ðPo0:05Þ higher concentrations of lead and cadmium in hair than animals from the unpolluted locality (2.9970.27 and 0.5270.06 mg/ g). Cows reared around aluminum manufacturing plant (0.3370.02 mg/mL) and urban cum small-industrial units (0.4170.03 mg/mL) had significantly ðPo0:05Þ higher
Table 1 Lead and cadmium residues in blood (mg/mL) and hair (mg/g) in cattle reared around different industrial/urban areas Lead
Cadmium
Blood 1
Unpolluted area ðn ¼ 30Þ
6
Coal mining areas ðn ¼ 45Þ
4
Phosphate rock mining areas ðn ¼ 21Þ
2
Steel processing plant ðn ¼ 46Þ
3
Aluminum manufacturing plant ðn ¼ 25Þ
8
Urban cum industrial areas ðn ¼ 55Þ
7
Closed lead cum operational zinc smelter ðn ¼ 7Þ
5
Lead–zinc smelter ðn ¼ 88Þ
Hair a
0.0770.01 (0.00–0.25) 0.1470.01a (0.00–0.60) 0.1470.02a (0.03–0.31) 0.1970.02a (0.00–0.41) 0.3370.02b (0.22–0.48) 0.4170.03bc (0.00–0.99) 0.5070.11c (0.13–0.87) 0.9970.04d (0.17–2.77)
Blood a
2.9970.27 (1.18–6.85) 1.8270.14a (0.36–4.41) 2.5170.79a (0.26–14.34) 2.4170.19a (0.21–6.21) 2.0370.10a (1.10–3.00) 4.8470.51a (0.31–16.8) 11.7274.02b (5.22–34.24) 15.0970.85c (1.50–37.24)
Hair a
0.02570.002 (0.00–0.05) 0.03270.001a (0.01–0.07) 0.04570.003a (0.02–0.07) 0.12770.017b (0.00–0.41) 0.04470.002a (0.03–0.07) 0.03470.002a (0.00–0.07) 0.02770.005a (0.01–0.05) 0.04370.002a (0.01–0.10)
0.5270.06a (0.31–1.67) 0.5970.03a (0.20–1.04) 0.2070.02a (0.00–0.39) 0.5070.05a (0.00–1.34) 0.2470.02a (0.15–0.49) 0.2170.02a (0.00–0.52) 5.7272.75c (0.35–19.67) 2.6270.32b (0.52–12.41)
The values are expressed as mean7SE. Values with different superscripts between rows in a column vary significantly at ðPo0:05Þ. Values in parentheses indicate ranges.
ARTICLE IN PRESS R.C. Patra et al. / Ecotoxicology and Environmental Safety 66 (2007) 127–131
blood lead levels than control animals (0.0770.01 mg/mL). However, hair lead concentrations in cows from these two localities did not differ significantly ðP40:05Þ from animals reared in unpolluted areas. The higher blood lead level in cows in different localities was associated with enhanced lead level in soil and fodder. The soil lead concentration around lead smelter was 232.897127.63 mg/g ðn ¼ 2Þ as against control value of 28.6672.53 mg/g ðn ¼ 3Þ and that of fodder around lead–zinc smelter and aluminum processing plant was 19.06711.32 mg/g ðn ¼ 7Þ and 2.6570.43 mg/g ðn ¼ 10Þ, respectively, as against control fodder lead level of 2.0770.21 mg/g ðn ¼ 8Þ from unpolluted locality. The mean blood cadmium level in cows was significantly ðPo0:05Þ higher only around steel processing unit (0.12770.017 mg/mL). The fodder cadmium concentration in this industrial area was 0.17370.06 mg/g ðn ¼ 2Þ as compared to control value of 0.15270.01 mg/g ðn ¼ 8Þ. However, those animals had mean hair cadmium concentrations comparable to those of control animals. Fig. 1 shows a scatter plot of continuous data from 317 animals and quadratic regression with blood lead on the x axis and hair lead on the y axis. The increase in blood lead concentration was associated with an increase in its accumulation in hair. This was substantiated by the finding that blood lead had a strong positive correlation with hair lead (r ¼ 0:672, Po0:01) and there was a significant ðPo0:01Þ quadratic regression between these two parameters. The accumulation of cadmium in hair was also influenced by blood (r ¼ 0:309, Po0:01) and hair lead (r ¼ 0:610, Po0:01) concentrations. The scatter plot of continuous data on blood lead and hair cadmium concentrations revealed a significant ðPo0:05Þ quadratic regression between these two variables (Fig. 2). However,
HLEAD
40 Observed 30
Quadratic
20
10
0
-10 -0.5
0.0
0.5
1.0 1.5 BLLEAD
2.0
2.5
3.0
Fig. 1. Quadratic regression and scatter plot of continuous data from 317 animals from different polluted and unpolluted localities with blood lead (mg/mL) on x axis and hair lead (mg/g) on y axis.
129
HAIRCAD
30 Observed 20
Quadratic
10
0
-10 -0.5
0.0
0.5
1.0 1.5 BLLEAD
2.0
2.5
3.0
Fig. 2. Scatter plot of continuous data on blood lead (mg/mL) and hair cadmium (mg/g) concentrations from 317 animals from different polluted and unpolluted localities and quadratic regression between these two variables.
the hair cadmium concentration was found to be a poor indicator (r ¼ 0:070, P40:05) of blood cadmium level. 4. Discussion Lead and cadmium are common environmental pollutants that persist in the environment for a long period and can be detected in most tissues of living organisms (Doganoc, 1996). Kruslin et al. (1999) suggested that analysis of hair could be an alternative to classic methodology and invasive biopsy for detection of chronic heavy metal intoxications. The concentration of lead was found to be much greater in hair than in other tissues during a survey on lead and cadmium levels in different tissues from pigs in Hungary (Gyori et al., 2005). In the present investigation, the hair lead level was significantly higher around closed lead cum operational zinc smelter and lead–zinc smelter. This was associated with higher blood lead level and lead concentrations in fodder suggesting that chronic and continuous intake of toxic heavy metal pollutant through ingestion of contaminated fodder might have resulted in its higher blood level and increased accumulation in hair over a long period. Elevated lead concentration in the feathers has been suggested as an indicator of high exposure during its formation in Spanish imperial eagle and other raptors (Pain et al., 2005). Nowak and Chmielnicka (2000) suggested that lead concentration in hair from exposed people could serve as an environmental marker of exposure to this metal and recorded influence of hair lead on other elements such as iron, copper, calcium and zinc. Ward and Savage (1994) reported higher concentrations of lead, cadmium, zinc, copper, chromium and nickel in blood and hair from
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livestock around motorways. In the present study, enhanced cadmium accumulation was recorded in hair from cows with chronic exposure to pollutants only around lead–zinc smelters and closed lead cum operational zinc smelter where only blood lead but not cadmium level was significantly higher than respective control values. In a natural case of lead–cadmium poisoning in sheep, significantly higher levels of both elements were noticed in blood and hair (Liu et al., 1997). Mankovska (1984) reported higher levels of lead and cadmium in both hair and serum samples from cattle around iron foundry. However, the present study reports for the first time higher cadmium concentration in hair from cows around closed lead cum operational zinc smelter and lead–zinc smelting unit where blood cadmium concentration was statistically comparable to that of control animals. This might be due to the interaction of lead and cadmium and facilitated accumulation of cadmium in hair in the presence of higher lead levels in blood and hair. Nowak (1998) reported a strong positive correlation between cadmium and lead in hair from a nonindustrialized population in Poland. Significantly higher blood cadmium level around steel processing unit in the present study was not associated with enhanced ðP40:05Þ accumulation of cadmium in hair. There was a nonsignificant correlation between blood and hair cadmium suggesting that hair cadmium level is little influenced by its blood level. Gyori et al. (2005) also recorded a low correlation of cadmium concentrations between hair and other tissues. Higher cadmium intake alone through cadmium-chloride-supplemented diet resulted in higher cadmium level in kidneys and liver but not in hair (Tsuneishi et al., 1981). Hair is a keratin-rich tissue with abundance of cysteine residues, the sulfhydryl group of which binds with divalent cations such as lead and cadmium leading to their persistence in hair for a long period (Raab et al., 2002; Hasan et al., 2004). The quadratic regression between blood and hair lead and the scatter plot (Fig. 1) shows that continual increase in blood lead concentration was not associated with a proportionate increase in its accumulation in hair. This might be due to greater saturation of binding sites of lead in hair. Brabner et al. (1993) recorded an early rapid increase of lead concentration in blood and liver of lamb with daily experimental exposure to lead before reaching a plateau. Similarly, liver cadmium concentration (on dry matter basis) in heifers showed no further increase for a period of 160 days after a continuous exposure to cadmium chloride for 394 days at the dose rate of 5 mg/kg (Smith et al., 1991). However, reports are not available on lead accumulation in hair to compare with the present finding. 5. Conclusion It is concluded that lead and cadmium accumulation in hair were associated with higher blood lead concentration and hair lead influenced the hair cadmium accumulation. A
strong positive correlation in lead concentrations and a nonsignificant correlation in cadmium concentrations between blood and hair suggest that lead but not cadmium in hair can be used reliably to indicate contamination of blood in cattle. Acknowledgments The authors are thankful for financial support through Competitive Grant Project (NATP) provided by ICAR and to State Animal Husbandry Departments for their cooperation for collection of samples. References Brabner, J., Hall, J., Smith, S., Stark, B., Suttle, N.F., Sweet, N., 1993. Soil ingestion is an important pathway for the entry of potentially toxic elements from sewage sludge treated pasture into ruminants and the food chain. In: Allan, R.J., Nriagu, J.O. (Eds.), Proceedings of the Ninth International Conference on Heavy Metals in the Environment, vol. 1. CEP, Edinburgh, pp. 446–449. Doganoc, D.Z., 1996. Distribution of lead, cadmium and zinc in tissues of hens and chickens from Slovenia. Bull. Environ. Contam. Toxicol. 57, 932–937. Dwivedi, S.K., Swarup, D., Dey, S., Patra, R.C., 2001. Lead poisoning in cattle and buffalo near primary lead–zinc smelter in India. Vet. Hum. Toxicol. 43, 74–75. Gyori, Z., Kovacs, B., Daniels, P., Szabo, P., Phillips, C., 2005. Cadmium and lead in Hungarian porcine products and tissues. J. Sci. Food Agric. 85, 1049–1054. Hasan, M.Y., Kosanovic, M., Fahim, M.A., Adem, A., Petroianu, G., 2004. Trace metal profiles in hair samples from children in urban and rural region of the United Arab Emirates. Vet. Hum. Toxicol. 46, 119–121. IAEA, 1978. Activation analysis of hair as an indicator of contamination of man by environmental trace element pollutants. IAEA/RL/50, Vienna, Austria. Kruslin, E., Hodel, C.M., Schurgast, H., 1999. Progress in diagnosis of chronic toxic metal poisoning by hair analysis. Toxicol. Lett. 88, 84. Liu, Z.P., Ma, Zhuo., Li, W.F., Cheng, X.F., 1997. Studies on lead–cadmium poisoning in sheep. Chin. J. Vet. Sci. 17, 166–169. Mankovska, B., 1984. Concentration of manganese, lead and cadmium in feedstuffs, blood serum and hair of diary cows in the vicinity of a ferroalloy works. Pol’notiospodarrtvo 30, 745–749. Nowak, B., 1998. Contents and relationship of elements in human hair from a non-industrialized population in Poland. Sci. Total Environ. 209, 59–68. Nowak, B., Chmielnicka, J., 2000. Relationship of lead and cadmium to essential elements in hair, teeth and nails of environmentally exposed people. Ecotoxicol. Environ. Saf. 46, 265–274. Okada, I.A., Sakuma, A.M., Maid, F.D., Dovidemskas, S., Zenebon, O., 1997. Evaluation of lead and cadmium in milk due to environmental contamination in Paraiba valley region of South Estern Brazil. Raissade-Saude-Publica 31, 140–143. Pain, D.J., Meharg, A.A., Ferrer, M., Taggart, M., Penteriani, V., 2005. Lead concentrations in bones and feathers of the globally threatened Spanish imperial eagle. Biol. Conserv. 121, 603–610. Patra, R.C., Swarup, D., Naresh, R., Kumar, P., Sekhar, P., 2005. Cadmium level in blood and milk from animals reared around different polluting sources in India. Bull. Environ. Contam. Toxicol. 74, 1092–1097. Phillips, C., Gyori, Z., Kovacs, B., 2003. The effect of adding cadmium and lead alone or in combination to the diet of pigs on their growth,
ARTICLE IN PRESS R.C. Patra et al. / Ecotoxicology and Environmental Safety 66 (2007) 127–131 carcass composition and reproduction. J. Sci. Food. Agric. 83, 1357–1365. Quig, D., 1998. Cysteine metabolism and metal toxicity. Altern. Med. Rev. 3, 262–269. Raab, A., Hansen, H.R., Zhuang, L.Y., Feldmann, J., 2002. Arsenic accumulation and speciation analysis in wool from sheep exposed to arsenosugars. Talanta 58, 167–176. Smith, R.M., Leach, R.M., Muller, L.D., Griel, L.C., Baker, D.E., 1991. Effects of log term dietary cadmium chloride on tissue, milk and urine mineral concentrations of lactating dairy cows. J. Anim. Sci. 69, 4088–4096. Snedecor, G.W., Cochran, W.G., 1994. Statistical methods. Iowa State University Press, Ames, IA. Struempler, R.E., Larson, G.E., Rimland, B., 1985. Hair mineral analysis and disruptive behaviour in clinically normal young men. J. Learn. Disabil. 18, 609–612.
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Swarup, D., Patra, R.C., Naresh, R., Kumar, P., Shekhar, P., 2005. Blood lead levels in lactating cows reared around polluted localities; transfer of lead in to milk. Sci. Total Environ. 347, 106–110. Tsuneishi, E., Takeshita, K., Yoshida, S., Nishimura, K., 1981. Accumulation and excretion of dietary cadmium in cattle and survey of cadmium content in organs of cattle produced in Tohoku district. Bull. Tohoku Natl. Agric. Exp. Station 65, 157–165. Vahter, M., Marafante, E., 1983. Intracellular distribution and metabolic fate of arsenite and arsenate in mice and rabbits. Chem. Biol. Interact. 47, 29–44. Ward, N.I., Savage, J.M., 1994. Elemental status of grazing animals located adjacent to the London Orbital (M25) motorway. Sci. Total Environ. 147, 185–189. Wecker, L., Miller, S.B., Cochran, S.R., Dugger, D.L., Johnson, W.D., 1985. Trace elements concentrations in hair from autisitic children. J. Mental Def. Res. 29, 15–22.
Ecotoxicology and Environmental Safety 66 (2007) 127–131 www.elsevier.com/locate/ecoenv
Tail hair as an indicator of environmental exposure of cows to lead and cadmium in different industrial areas R.C. Patraa,, D. Swarupa, Ram Nareshb, Puneet Kumara, D. Nandia, Pallav Shekhara, S. Royc, S.L. Alic a
Environmental Medicine Laboratory, Division of Medicine, Indian Veterinary Research Institute, Izatnagar 243 122, UP, India b Division of Animal Health, IVRI Regional Center at Mukteswar, Nainital, Uttaranchal, India c Division of Clinical Medicine, College of Veterinary Science and Animal Husbandry, Anjora, Durg, Chattisgarh, India Received 22 May 2005; received in revised form 8 January 2006; accepted 22 January 2006 Available online 23 March 2006
Abstract This study examines the use of tail hair from cows as a possible biomarker of environmental exposure to lead and cadmium around different industrial areas. Respective blood and tail hair samples were collected from a total of 317 apparently healthy cows above 3 years of age. This includes 287 cows reared in industrial and urban areas and 30 cows from areas free from polluting sources. Significantly ðPo0:05Þ higher lead and cadmium residues were recorded in hair from cows reared around lead–zinc smelter and closed lead cum operational zinc smelter. However, cows from those areas had significantly ðPo0:05Þ higher blood lead but not cadmium concentration as compared to respective control value. Although mean blood lead concentration in cows around aluminum processing plant and urban cum small industrial areas and that of cadmium around steel processing plant were significantly ðPo0:05Þ higher than respective control, the mean hair lead and cadmium content remained statistically ðP40:05Þ comparable to that of respective control values. The blood lead was significantly correlated with hair lead ðr ¼ 0:672, Po0:01Þ and cadmium ðr ¼ 0:309, Po0:05Þ. There was a significant correlation between lead and cadmium concentration ðr ¼ 0:610, Po0:01Þ in hair and a nonsignificant correlation between blood and hair cadmium suggesting that cadmium accumulation in hair was influenced by blood and hair lead concentrations in cows environmentally exposed to lead. r 2006 Elsevier Inc. All rights reserved. Keywords: Lead; Cadmium; Tail hair; Cow; Blood
1. Introduction Environmental pollution due to toxic heavy metals has gained widespread attention due to its various deleterious health effects in man and other animals. Lead and cadmium are the two most abundant toxic metals in the environment with no detectable beneficial biological roles. The common sources of lead and cadmium are diverse in nature including natural and anthropogenic processes such as combustion of coal and mineral oil, smelters, mining, alloy processing units, paint industries, etc. (Dwivedi et al., 2001; Phillips et al., 2003; Patra et al., 2005; Swarup et al., Corresponding author. Fax: +91 581 2303284.
E-mail addresses: (R.C. Patra).
[email protected],
[email protected]
0147-6513/$ - see front matter r 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.ecoenv.2006.01.005
2005). These anthropogenic activities and vehicular emissions contribute to the entry of toxic metals to human’s and other animal’s food chains (Okada et al., 1997). Chronic exposure to these sulfhydryl reactive metals through various routes results in their higher accumulation in tissues, bones, hair and blood, and monitoring of these toxic metals in biological materials essentially indicates the status of environmental degradation (Quig, 1998; Phillips et al., 2003; Raab et al., 2002; Vahter and Marafante, 1983). Hair fiber is a metabolically dead material after it leaves the epidermis. However, the fiber in the root during its growth is metabolically very active. Higher arsenic level in wool fiber has been reported in sheep fed with a higharsenic diet as it is readily taken up by the cells of the root (Raab et al., 2002). This signifies the role of hair fiber in
ARTICLE IN PRESS R.C. Patra et al. / Ecotoxicology and Environmental Safety 66 (2007) 127–131
128
diagnosis of chronic exposure and past poisonings of certain metals. Hair samples have been used for noninvasive diagnosis of cadmium toxicity in humans (Struempler et al., 1985). The frequency of diseases such as autism has been predicted in humans using data on hair concentrations of cadmium and other minerals (Wecker et al., 1985). It is therefore hypothesized that the tail hair from cattle reared around industrial areas may serve as a tool for monitoring exposure to heavy metal pollutants such as lead and cadmium. 2. Material and methods 2.1. Animals Cows ðn ¼ 287Þ above 3 years of age, reared and allowed to graze on pasture within 2 km of industrial units, were used for this study. The industrial units in various parts of India included coal mining ðn ¼ 45Þ, rock phosphate mining cum phosphate fertilizer plant ðn ¼ 21Þ, steel processing unit ðn ¼ 46Þ, urban areas with small industrial units ðn ¼ 55Þ, aluminum processing plant ðn ¼ 25Þ, closed lead cum operational zinc smelter ðn ¼ 7Þ, and lead–zinc smelter ðn ¼ 88Þ. Samples were also collected from 30 cows of identical age which were reared in areas apparently free from industrial or urban polluting sources to serve as controls.
2.2. Sampling Surveys were carried out over a period of 3 years from 2002 to 2005. Respective blood and hair samples were collected from each animal with the consent of the animal’s owners. About 5 mL blood samples were collected by jugular venepuncture into nitric-acid-washed heparinized glass vials. Hair samples were collected from the tail switch using a scalpel and kept in separate plastic bags. Samples of soil and fodder, provided to the cows, were collected in polythene bags for further processing. The blood samples were stored at 4–8 1C. Soil, hair and fodder samples were stored at room temperature until wet digestion within a period of 1 week from collection of samples.
2.3. Analysis of lead and cadmium Hair samples were washed sequentially with acetone, distilled water, and acetone to remove adherent dirt and organic materials (IAEA, 1978) and fodder samples were washed by deionized water. Approximately, 1 g each of the hair sample after drying, 5 mL of blood, 5 g of fodder, and 1 g of soil sample were wet digested with nitric and perchloric acid mixture (3:1 v/v) at low heat (o90 1C). Two to three blank samples were run simultaneously with each batch of the digestion where biosample was substituted by deionized triple-distilled water. Lead and cadmium concentrations in digested samples were estimated after suitable dilution using an atomic absorption spectrophotometer (Electronic Corp. of India, Ltd.) at the wavelengths of 217 nm (detection limit, 0.025 mg/mL) and 229.5 nm (detection limit, 0.005 mg/mL), respectively, with 6-mA current and the values were expressed in mg/mL of blood and mg/g of hair, fodder, or soil (dry weight basis).
2.4. Analysis of data The data were analyzed using one-way analysis of variance to compare the mean values and are expressed as mean7SE throughout the text. The correlation between blood and hair concentrations of lead and cadmium were analyzed using standard statistical methods (Snedecor and Cochran, 1994).
3. Results Table 1 shows the lead and cadmium concentrations in blood and hair from cows ðn ¼ 317Þ reared in different industrial/urban and unpolluted areas. Cows in the vicinity of only lead–zinc smelter (15.0970.85 and 2.6270.32 mg/g) and closed lead cum operational zinc smelter (11.7274.02 and 5.7272.75 mg/g) had significantly ðPo0:05Þ higher concentrations of lead and cadmium in hair than animals from the unpolluted locality (2.9970.27 and 0.5270.06 mg/ g). Cows reared around aluminum manufacturing plant (0.3370.02 mg/mL) and urban cum small-industrial units (0.4170.03 mg/mL) had significantly ðPo0:05Þ higher
Table 1 Lead and cadmium residues in blood (mg/mL) and hair (mg/g) in cattle reared around different industrial/urban areas Lead
Cadmium
Blood 1
Unpolluted area ðn ¼ 30Þ
6
Coal mining areas ðn ¼ 45Þ
4
Phosphate rock mining areas ðn ¼ 21Þ
2
Steel processing plant ðn ¼ 46Þ
3
Aluminum manufacturing plant ðn ¼ 25Þ
8
Urban cum industrial areas ðn ¼ 55Þ
7
Closed lead cum operational zinc smelter ðn ¼ 7Þ
5
Lead–zinc smelter ðn ¼ 88Þ
Hair a
0.0770.01 (0.00–0.25) 0.1470.01a (0.00–0.60) 0.1470.02a (0.03–0.31) 0.1970.02a (0.00–0.41) 0.3370.02b (0.22–0.48) 0.4170.03bc (0.00–0.99) 0.5070.11c (0.13–0.87) 0.9970.04d (0.17–2.77)
Blood a
2.9970.27 (1.18–6.85) 1.8270.14a (0.36–4.41) 2.5170.79a (0.26–14.34) 2.4170.19a (0.21–6.21) 2.0370.10a (1.10–3.00) 4.8470.51a (0.31–16.8) 11.7274.02b (5.22–34.24) 15.0970.85c (1.50–37.24)
Hair a
0.02570.002 (0.00–0.05) 0.03270.001a (0.01–0.07) 0.04570.003a (0.02–0.07) 0.12770.017b (0.00–0.41) 0.04470.002a (0.03–0.07) 0.03470.002a (0.00–0.07) 0.02770.005a (0.01–0.05) 0.04370.002a (0.01–0.10)
0.5270.06a (0.31–1.67) 0.5970.03a (0.20–1.04) 0.2070.02a (0.00–0.39) 0.5070.05a (0.00–1.34) 0.2470.02a (0.15–0.49) 0.2170.02a (0.00–0.52) 5.7272.75c (0.35–19.67) 2.6270.32b (0.52–12.41)
The values are expressed as mean7SE. Values with different superscripts between rows in a column vary significantly at ðPo0:05Þ. Values in parentheses indicate ranges.
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blood lead levels than control animals (0.0770.01 mg/mL). However, hair lead concentrations in cows from these two localities did not differ significantly ðP40:05Þ from animals reared in unpolluted areas. The higher blood lead level in cows in different localities was associated with enhanced lead level in soil and fodder. The soil lead concentration around lead smelter was 232.897127.63 mg/g ðn ¼ 2Þ as against control value of 28.6672.53 mg/g ðn ¼ 3Þ and that of fodder around lead–zinc smelter and aluminum processing plant was 19.06711.32 mg/g ðn ¼ 7Þ and 2.6570.43 mg/g ðn ¼ 10Þ, respectively, as against control fodder lead level of 2.0770.21 mg/g ðn ¼ 8Þ from unpolluted locality. The mean blood cadmium level in cows was significantly ðPo0:05Þ higher only around steel processing unit (0.12770.017 mg/mL). The fodder cadmium concentration in this industrial area was 0.17370.06 mg/g ðn ¼ 2Þ as compared to control value of 0.15270.01 mg/g ðn ¼ 8Þ. However, those animals had mean hair cadmium concentrations comparable to those of control animals. Fig. 1 shows a scatter plot of continuous data from 317 animals and quadratic regression with blood lead on the x axis and hair lead on the y axis. The increase in blood lead concentration was associated with an increase in its accumulation in hair. This was substantiated by the finding that blood lead had a strong positive correlation with hair lead (r ¼ 0:672, Po0:01) and there was a significant ðPo0:01Þ quadratic regression between these two parameters. The accumulation of cadmium in hair was also influenced by blood (r ¼ 0:309, Po0:01) and hair lead (r ¼ 0:610, Po0:01) concentrations. The scatter plot of continuous data on blood lead and hair cadmium concentrations revealed a significant ðPo0:05Þ quadratic regression between these two variables (Fig. 2). However,
HLEAD
40 Observed 30
Quadratic
20
10
0
-10 -0.5
0.0
0.5
1.0 1.5 BLLEAD
2.0
2.5
3.0
Fig. 1. Quadratic regression and scatter plot of continuous data from 317 animals from different polluted and unpolluted localities with blood lead (mg/mL) on x axis and hair lead (mg/g) on y axis.
129
HAIRCAD
30 Observed 20
Quadratic
10
0
-10 -0.5
0.0
0.5
1.0 1.5 BLLEAD
2.0
2.5
3.0
Fig. 2. Scatter plot of continuous data on blood lead (mg/mL) and hair cadmium (mg/g) concentrations from 317 animals from different polluted and unpolluted localities and quadratic regression between these two variables.
the hair cadmium concentration was found to be a poor indicator (r ¼ 0:070, P40:05) of blood cadmium level. 4. Discussion Lead and cadmium are common environmental pollutants that persist in the environment for a long period and can be detected in most tissues of living organisms (Doganoc, 1996). Kruslin et al. (1999) suggested that analysis of hair could be an alternative to classic methodology and invasive biopsy for detection of chronic heavy metal intoxications. The concentration of lead was found to be much greater in hair than in other tissues during a survey on lead and cadmium levels in different tissues from pigs in Hungary (Gyori et al., 2005). In the present investigation, the hair lead level was significantly higher around closed lead cum operational zinc smelter and lead–zinc smelter. This was associated with higher blood lead level and lead concentrations in fodder suggesting that chronic and continuous intake of toxic heavy metal pollutant through ingestion of contaminated fodder might have resulted in its higher blood level and increased accumulation in hair over a long period. Elevated lead concentration in the feathers has been suggested as an indicator of high exposure during its formation in Spanish imperial eagle and other raptors (Pain et al., 2005). Nowak and Chmielnicka (2000) suggested that lead concentration in hair from exposed people could serve as an environmental marker of exposure to this metal and recorded influence of hair lead on other elements such as iron, copper, calcium and zinc. Ward and Savage (1994) reported higher concentrations of lead, cadmium, zinc, copper, chromium and nickel in blood and hair from
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livestock around motorways. In the present study, enhanced cadmium accumulation was recorded in hair from cows with chronic exposure to pollutants only around lead–zinc smelters and closed lead cum operational zinc smelter where only blood lead but not cadmium level was significantly higher than respective control values. In a natural case of lead–cadmium poisoning in sheep, significantly higher levels of both elements were noticed in blood and hair (Liu et al., 1997). Mankovska (1984) reported higher levels of lead and cadmium in both hair and serum samples from cattle around iron foundry. However, the present study reports for the first time higher cadmium concentration in hair from cows around closed lead cum operational zinc smelter and lead–zinc smelting unit where blood cadmium concentration was statistically comparable to that of control animals. This might be due to the interaction of lead and cadmium and facilitated accumulation of cadmium in hair in the presence of higher lead levels in blood and hair. Nowak (1998) reported a strong positive correlation between cadmium and lead in hair from a nonindustrialized population in Poland. Significantly higher blood cadmium level around steel processing unit in the present study was not associated with enhanced ðP40:05Þ accumulation of cadmium in hair. There was a nonsignificant correlation between blood and hair cadmium suggesting that hair cadmium level is little influenced by its blood level. Gyori et al. (2005) also recorded a low correlation of cadmium concentrations between hair and other tissues. Higher cadmium intake alone through cadmium-chloride-supplemented diet resulted in higher cadmium level in kidneys and liver but not in hair (Tsuneishi et al., 1981). Hair is a keratin-rich tissue with abundance of cysteine residues, the sulfhydryl group of which binds with divalent cations such as lead and cadmium leading to their persistence in hair for a long period (Raab et al., 2002; Hasan et al., 2004). The quadratic regression between blood and hair lead and the scatter plot (Fig. 1) shows that continual increase in blood lead concentration was not associated with a proportionate increase in its accumulation in hair. This might be due to greater saturation of binding sites of lead in hair. Brabner et al. (1993) recorded an early rapid increase of lead concentration in blood and liver of lamb with daily experimental exposure to lead before reaching a plateau. Similarly, liver cadmium concentration (on dry matter basis) in heifers showed no further increase for a period of 160 days after a continuous exposure to cadmium chloride for 394 days at the dose rate of 5 mg/kg (Smith et al., 1991). However, reports are not available on lead accumulation in hair to compare with the present finding. 5. Conclusion It is concluded that lead and cadmium accumulation in hair were associated with higher blood lead concentration and hair lead influenced the hair cadmium accumulation. A
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