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Daily intake of manganese by the adult population of Mumbai
The Science of the Total Environment 250 Ž2000. 43᎐50
Daily intake of manganese by the adult population of Mumbai R.M. TripathiU , Suchismita Mahapatra, Radha Raghunath, V.N. Sastry, T.M. Krishnamoorthy En¨ ironmental Assessment Di¨ ision, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India Received 14 September 1999; accepted 19 December 1999
Abstract The daily intake of manganese ŽMn. estimated through air, water and duplicate dietary analysis is found to range from 0.67 to 4.99 mg with a mean value of 2.21 mg. Ingestion through food contributed to the predominant fraction of the intake. The turnover rate of Mn through blood is approximately 2 h, based on the mean concentration of Mn in blood of 1.54 g ly1. The average concentrations of Mn in water and air were approximately 1.42 g ly1 and 37 ng my3, respectively. The daily intake of Mn by the adult population of Mumbai is closer to the lower bound of the recommended limit of 2᎐5 mg. Electro Thermal Atomic Absorption Spectrophotometry ŽET-AAS., has been used for the determination of Mn in a variety of environmental and human biological fluids. The detection limit of Mn for a volume injection of 20 l is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities Ž0.5᎐10 ppm. and is found to be within "8%. The reliability of estimation is further assessed through the analysis of Standard Reference Materials ŽSRMs. of soil, hay, milk powder and fish tissue obtained from IAEA. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Mn; Blood; Dietary intake; Ingestion; ET-AAS
1. Introduction Man’s essential requisites of air, water and food contain trace amounts of a wide range of
U
Corresponding author. E-mail address: [email protected] ŽR.M. Tripathi.
heavy metals, some of them have a significant role in several biochemical processes, whereas others are contaminants ŽPirrone and Keeler, 1996; Raghunath et al., 1997; Tripathi et al., 1999.. Manganese is an essential trace element for humans to maintain normal metabolism. Manganese intake through food must be, in general, sufficient to prevent deficiency ŽDonna and
0048-9697r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 0 . 0 0 3 6 0 - 0
44
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
Baldwin, 1997.. The best-defined deficiency symptom observed in animals relate to skeletal abnormalities where the organic matrix of bones and cartilage tend to be poorly developed ŽFardy et al., 1992.. Manganese is subjected to delicate homeostatic control and approximately 3᎐5% of ingested Mn is absorbed and it is rapidly cleared from the blood through the liver. It has been established that the whole blood Mn is a valid indicator of body Mn status and can be used for the diagnosis of diseases when the metabolism of trace element is disrupted ŽGreger, 1998.. At a lower level, manifestations of Mn deficiency occur while high levels of Mn exposure are associated with neurologic and neuropsychiatric disorders ŽDonna, 1999.. Chronic exposure to Mn causes neurophysiological abnormalities ŽKaji et al., 1993.. Thus, the information on the intake levels of Mn is important in assessing the risk to human health. Due to its very low concentrations in a variety of environmental and biological samples such as air, water, food, serum and urine; any analysis requires the use of an accurate analytical method with sufficient sensitivity. The sensitivities offered by methods such as energy dispersive X-ray fluorescence ŽEDXRF., atomic emission spectrometry with inductively coupled plasma excitation ŽAES-ICP. are not sufficient for accurate determination of Mn at concentrations usually encountered in biological samples ŽWillium, 1998; GBC, 1994.. The ET-AAS technique offers the required sensitivity levels and can determine Mn in biological sample matrices in parts per billion levels. The purpose of this study is to standardize a reliable method for the determination of Mn in a variety of environmental materials such as water, air particulate, duplicate diet, blood and urine for estimating its daily intake and turn over rate in the adult population of Mumbai.
2. Experimental 2.1. Sampling locations Samples were collected from different locations in Mumbai viz. Mahim, Bandra, Shivaji park,
Dadar, Anushaktinagar and Vashi during 1998᎐1999. Blood, duplicate diet, urine, drinking water and milk samples were collected from each location from volunteers of middle class families who were not exposed to Mn source. 2.2. Sample collection and processing 2.2.1. Air Air particulate samples were collected for durations of 24 h on Whatman EPM 2000 filter papers at a flow rate of 1000 l miny1 using a high volume sampler. Average flow rate was taken into account for calculation of the volume of the air sampled. Air particulate samples collected on filter papers were wet digested with a mixture of electronic grade nitric acid, hydrochloric acid and perchloric acid. The residue was taken up in 10 ml of 0.25% nitric acid. Filter paper blanks and acid blanks were also taken through the same procedure simultaneously. 2.2.2. Duplicate diet In order to study the dietary intake of Mn by the Mumbai adult population, 60 samples of ‘duplicate diet’ were collected. They were weighed and homogenized in the laboratory. A known weight of sample Ž; 20 g. was dry ashed at a temperature of 400⬚C. The ashed sample was then treated with 1 ml electronic grade nitric acid and the residue was dissolved in 10 ml of 0.25% HNO3 . The details of sample collection and processing are given elsewhere ŽTripathi et al., 1997.. 2.2.3. Blood Blood samples of 1 ml were collected from adults Žwith no occupational Mn exposure. residing in different parts of Mumbai with special care by vein puncture into heparinized pretreated clean polypropylene tubes. Serum samples Ž1 ml. were separated from clotted blood. The blood Žwhole blood. and serum samples were wet digested in duplicate with electronic grade nitric acid and perchloric acid. Digested samples were made up to 2 ml using 0.25% nitric acid. Extreme care was taken to avoid any contamination during sample collection and processing. Reagent blanks were also taken simultaneously using the same proce-
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
dure. The details of sample collection and processing are given elsewhere ŽRaghunath et al., 1999.. Drinking water, milk and urine samples were collected in pretreated polypropylene containers. The details of collection and processing of water, urine and milk are given in our earlier publications ŽRaghunath et al., 1997; Tripathi et al., 1999.. 2.3. Reagents All chemicals used were Merck, Suprapur, Analar or electronic grade. Reagents used for wet ashing were concentrated nitric acid ŽElectronic grade. and perchloric acid ŽSuprapur grade.. Standard stock solution Ž0.01 M. of Mn was prepared and necessary dilutions were made as and when required. 2.3.1. Precautions Quartz, Teflon and high purity polyethylene containers have been used for collection, decomposition and storage of samples prior to analysis. In the present study, all laboratory wares used in sample collection, ashing, analysis and storage were soaked in 10% HNO3 for several days and then rinsed thoroughly with distilled and double distilled water, respectively, before use. Reagent blanks were taken along with each batch of sample and the Mn concentration observed in these blank samples were subtracted from the corresponding batch of field samples. Blank samples always showed extremely low levels of Mn Ž- 4 pg absolute..
45
2.4. Instrumentation A GBC-904 atomic absorption spectrophotometer and GF-3000 automated graphite furnace system were used. The system comprises GF-3000 graphite furnace and PAL-3000 programmable automatic sampler. This combination of equipment is particularly suited for trace analysis since the PAL-3000 can automatically prepare a range of standards from a single stock solution, inject a chemical modifier and even automatically prepare a series of standard additions. A deuterium lamp background corrector was used in all instances. A GBC hollow cathode lamp was used as a light source. The operating conditions are described below: Operating conditions for manganese determination by ETAAS Atomization Analytical line Žnm. Slit width Žnm. Lamp current ŽmA. Absorbance measurement mode Sampling mode Sample injection Calibration method
Furnace 279.5 0.2 9.0 Peak area Auto Sampling Volume 20 l Auto calculated
The furnace conditions were set to give complete drying of the sample without boiling. The ashing temperature of 700⬚C was found to yield the maximum absorbance. The operating graphite furnace program is given in Table 1.
Table 1 Temperature program of graphite furnace Step
Final temp. Ž⬚C.
Ramp time Žs.
Hold time Žs.
Gas type
Read
Signal graphics
1 2 3 4 5 6 7
40 100 120 700 700 2400 2500
10 10 10 10 0.2 1 1
5 10 10 10 1 1 1
None Inert Inert Inert None None Inert
Off Off Off Off Off On Off
Off Off Off Off Off On Off
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
46
3. Results and discussion
Table 2 Concentrations of Mn in standard reference materials
3.1. Interference study
S.N.
Reference material
Unit
Observed value Ž7 replicates.
Certified value
The precision of the procedure was established by analyzing Mn in synthetic samples containing different elements such as Pb, Cd, Cu, Zn, Cr, Co, Ni, In, Tl, Fe, Sn, Ti, Bi, Se and Mg in different quantities Ž0.5᎐10 ppm.. The recovery of Mn was established by determining the added Mn contents in the synthetic samples. The results demonstrate that the recovery of the Mn is quantitative and no interference was observed due to the presence of other elements.
1
Soil-7 IAEA S-7 Hay IAEA V-10 Milk powder IAEA A᎐11 Fish tissue MA-B-3rTM
g gy1
626 Ž624᎐630. 44 Ž42᎐47. 255 Ž252᎐257. 2.57 Ž2.45᎐2.73.
631 Ž604᎐650. 47 Ž32᎐52. 257 Ž248᎐266. 2.62 Ž2.22᎐3.03.
2 3 4
g gy1 ng gy1 g gy1
3.3. Concentrations of Mn in different en¨ ironmental matrices
3.2. Quality assurance The mean concentration of Mn in air particulate, serum, blood, urine, cow milk, human milk, drinking water and duplicate diet samples along with range are given in Table 3. The reported data is based upon a number of measurements.
The reliability of the procedure for estimation of Mn in environmental and biological samples by ET-AAS has been further assessed by analyzing the standard reference materials such as soil-7, milk powder ŽA-11., fish tissue ŽMA-B-3rTM. and hay ŽV-10. obtained from the International Atomic Energy Agency. The results agree within "7% with certified values ŽTable 2.. The validity of the method was further ascertained by crossmethod checks, spike recovery and replicate analysis. The detection limit of Mn for a volume injection of 20 l is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities Ž0.5᎐10 ppm. and is found to be within "8%.
3.4. Mn concentrations in air
The Mn levels in air particulate samples collected from Mumbai were found to vary from 15᎐65 ng my3 with a mean of 37 ng my3 . Negi et al. Ž1987. have reported a value of 46 ng my3 for Mumbai atmosphere. Loranger and Zayed Ž1997. have reported the respirable and total Mn air-
Table 3 Concentrations of Mn in different environmental and biological matrices S.N.
1 2 3 4 5 6 7 8
Matrix
Serum Whole blood Urine Air particulate Cow milk Human milk Drinking water Duplicate diet
No. of samples
Unit
35 60 20 15 30 25 15 60
ng ml y1 ng ml y1 ng ml y1 ng my3 ng ml y1 ng ml y1 ng ml y1 mg d y1
Mn concentration Mean
Min
Max
0.45 1.54 0.3 37 1.13 1.0 1.42 2.21
0.11 0.70 0.15 15 0.37 0.69 1.1 0.67
1.2 4.3 1.9 65 3.2 1.8 2.9 4.99
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
47
borne concentrations at Montreal to be 24 and 50 ng my3 , respectively. 3.5. Mn concentrations in drinking water The levels of Mn in drinking water at Mumbai was found to vary from 1.1 to 2.9 ng mly1 with a mean of 1.42 ng mly1 , which is much lower than the stipulated drinking water standards of 2 ppm by the Bureau of Indian Standards ŽBIS, 1998.. As far as is known, humans suffer no harmful effects from drinking water containing manganese. Levels of Mn become depleted when exposed to the air owing to the oxidation of Mnq2 to Mnq4 state, which eventually precipitates as oxide form. The rates of oxidation are not rapid and thus reduced forms can persist for sometime in aerated waters. This is especially true when the pH is below 9. The rates may be increased by the presence of some inorganic catalysts or through the action of certain microorganisms. 3.6. Mn le¨ els in blood The levels of Mn in serum were found to vary from 0.11 to 1.2 ng mly1 while the same in whole blood varied between 0.7 and 4.3 ng mly1 . The frequency distribution of Mn levels in blood samples is shown in Fig. 1. It is seen from the figure that the maximum percentage Ž40%. of the population have Mn blood levels between 0.75 and Table 4 Mn levels in blood reported in different countries S.N. Country
1 2 3 4 5 6 7
USA
Concentration Reference Žng mly1 .
1.2 Ž0.7᎐2.0. Canada 7.2 Belgium 5.7 Ž0.4᎐13.1. Netherlands 0.63 Ž0.54᎐1.76. Australia 2.0 India 1.54 Ž0.7᎐4.3. Threshold value 10
Willium Ž1998. Donna et al. Ž1994. Roels et al. Ž1987a. Woittiez and Iyengar Ž1988. GBC Ž1994. Present study Ž1999. Roels et al. Ž1987b.
Fig. 1. Frequency distribution of Mn in blood in Mumbai during 1999.
1.25 ng mly1 . For comparison, the concentrations of Mn in blood reported from different countries are given in Table 4. It is evident from the table that the Mn blood levels reported for USA, Netherlands and Australia are comparable to the values observed in the present study. The Mn levels in the blood of the adult population of Mumbai is lower than the threshold level of 10 ng mly1 suggested by Roels et al. Ž1987a,b.. 3.7. Mn le¨ els in urine The mean concentrations of Mn in urine samples were observed as 0.3 ng mly1 in the adult population of Mumbai Žrange s 0.15᎐1.9 ng mly1 . and this is comparable with the value of 0.62 ng mly1 reported for adults in Canada ŽDonna et al., 1994.. Daniel Ž1998. have reported urine Mn levels as 0.2 ng mly1 for residents of the USA. 3.8. Mn in duplicate diet The daily intake depends both on the concentration of Mn in the food materials and the amount consumed. The main food of the Indian population is rice or wheat and hence concentration of Mn in cereals contribute a major part to the total daily intake. The daily consumption of fruits, meat and milk is generally much less compared to cereals and pulses and hence their con-
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
48
tribution to the total daily intake of Mn is quite low. The Mn concentrations in human milk ranged between 0.69 and 1.8 ng mly1 and this is lower than 4 y 8 ng mly1 reported by Lonnerdal Ž1997. for California. The daily dietary intake of Mn was estimated by ‘duplicate diet’ analysis which was based on the analysis of cumulative food including liquid food Že.g. tea, coffee, milk, water, etc.. consumed during 24 h. The dietary intake of Mn varied between 0.67 and 4.99 mg dayy1 with a mean of 2.21 mg dayy1 . The variations in daily intake of Mn through duplicate diet in different suburbs of Mumbai is given in Table 5. The dietary intake of Mn by the population dwelling in Dadar and Anushaktinagar suburbs was relatively higher compared to that of other areas, however, no specific reason could be attributed to this fact. An attempt was also made to study the Mn dietary intake through vegetarian Ž2.21 mg dayy1 .rnon-vegetarian Ž2.19 mg dayy1 . diet, however, no significant difference was observed during this study. It has been reported ŽFardy et al., 1992; Nielsen, 1994. that the Mn intake through a vegetarian diet is more than that of a non-vegetarian diet since cereals Ž2.48 mg dayy1 ., leafy vegetables Ž0.12 mg dayy1 . and tea Ž690 g dayy1 . are rich in Mn compared to meat Ž0.008 mg dayy1 ., fish Ž0.011 mg dayy1 . and dairy Table 5 Dietary intake of Mn for different areas in Mumbai S.N.
Place
No. of samples
G.M. Žmg dayy1 .
GSD
1 2 3 4 5 6
Mahim Bandra Shivaji park Dadar Anushaktinagar Vashi
14 11 9 6 9 11
2.46 2.09 1.68 3.75 3.91 1.07
1.65 2.11 1.39 1.21 1.26 1.13
Fig. 2. Frequency distribution of dietary intake of Mn by the population of Mumbai.
products Ž0.005 mg dayy1 .. The frequency distribution of Mn levels in duplicate diet samples ŽFig. 2. reflects that the maximum percentage Ž32%. of the population have the dietary intake between 1.5 and 2.25 mg dayy1 . 3.9. Daily total intake through inhalation and ingestion The daily total intake of Mn through inhalation and ingestion of water and food is shown in Table 6. The air borne Mn levels varied between 15 and 65 ng my3 in the atmosphere of Mumbai. The daily intake of Mn contribution through inhalation worked is in the range of 0.3᎐1.3 g Žor 0.004᎐0.018 g kgy1 . based on a 20 m3 air intake for a 70-kg adult. Loranger and Zayed Ž1997. have reported the daily intake of Mn through inhalation as 0.001᎐0.05 g kgy1 for the Canadian population which is slightly higher than that observed during this study.
Table 6 Daily intake of Mn by the Mumbai adult population Source
Daily requirement
Mn concentration
Total daily intake
Absorption fraction Ž%.
Daily uptake Žg.
Air Water Food Total
20 m3 2.0 l ᎐
37 ng my3 1.42 g l y1 2.21 mg dy1
0.74 g 2.84 g 2.21 mg 2.21 mg
50 5 5 ᎐
0.37 0.142 110.5 111.0
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50 Table 7 Daily intake of Mn in different countries S.N.
Country
mg dy1
Reference
1 2 3 4 5 6 7
USA Germany Belgium UK Australia India ESADDIa
2.4 2.7 2.6 4.6 2.96 2.23 2᎐5
Mumcu and Aras Ž1988. Mumcu and Aras Ž1988. Buchet and Lauwenys Ž1983. Mumcu and Aras Ž1988. Fardy et al. Ž1992. Present study Ž1999. Greger Ž1998.
a
Estimated safe and adequate daily dietary intake.
The total intake of Mn through the duplicate diet study was 2.21 mg dayy1 which is closer to the lower bound of recommended intake value of 2᎐5 mg dayy1 given by the Food and Nutrition Board ŽFardy et al., 1992.. The intake of Mn via inhalation route is much lower compared to the ingestion pathway. The net uptake of Mn through inhalation and ingestion pathways works out to be 0.111 mg dayy1 . This daily total intake of Mn by the Mumbai adult population is comparable ŽTable 7. with the reported values for some countries like USA, Belgium and Germany, however, it is closer to the lower bound of the Provisional Tolerable Daily Intake Value ŽGreger, 1998.. Tea extract contain high levels of manganese, approximately 2300 g ly1 ŽFardy et al., 1992. and a significant increase of approximately 21᎐45% in the daily intake of manganese for adults could occur when tea contributions are included in the diet. 3.10. Turno¨ er rate of Mn The turnover rate Ž1r . of ingested Mn has been calculated using the single component first order kinetics relating intake and steady concentration of Mn in blood as reported below: dcrdt s fI y CV where, C s concentration of Mn in blood Žg ly1 ., f s fractional uptake Ž5%., I s daily intake of Mn Žmg dayy1 ., V s volume of blood in the body Ž5.2 l. and s elimination rate constant. The turnover rate of ingested Mn in blood under steady state condition works out to be
49
approximately 2 h based on the observed mean concentration of Mn in blood as 1.54 g ly1 and the daily intake of Mn as 2.21 mg.
4. Conclusions The dietary intake of Mn for the Mumbai adult population was found to be 2.21 mg dayy1 , which is within the recommended daily intake. The ingestion pathway was found to be the main route of Mn uptake by adults. The average concentration in the atmosphere of Mumbai was found to be 37 ng my3 . The Mn levels in blood of adult population in Mumbai City was found to be 1.54 ng mly1 , which is lower than the threshold level. The frequency distribution pattern of dietary intake indicates values between 1.5 and 3 mg dayy1 for more than 50% of the study group. References BIS. Packaged natural mineral water ᎏ specifications. Bureau of Indian Standards, 1998;IS:13428. Buchet JP, Lauwenys R. Oral daily intake of Cd, Pb, Mn, Cu, Cr, Hg, Ca, Zn, As in Belgium: a duplicate meal study. Food Chem Toxicol 1983;21:19᎐24. Daniel CP. Trace metals in urine of United States residents: reference range concentrations. Environ Res 1998;76: 53᎐59. Donna M, Huel G, Bowler R, Baldwin M, Robert T, Martin L. Nervous system dysfunction among workers with long term exposure to Mn. Environ Res 1994;64:151᎐180. Donna M, Baldwin M. Early manifestations of Mn neuro toxicity in humans: an update. Environ Res 1997;73:92᎐100. Donna M. Neurotoxic effects of low level exposure to Mn in human populations. Environ Res 1999;80A:99᎐102. Fardy JJ, McOrist GD, Farrar YJ. The determination of Mn status in the Australian diet using neutron activation analysis. J Radioanal Nucl Chem 1992;163:195᎐203. GBC Ž1994.. Graphite furnace methods manual ᎏ application of System FG-2000r3000. GBC Scientific Equipment Pty Ltd, Australia 1994. Greger JL. Dietary standards for Mn: overlap between nutritional and toxicological studies. J Nutr 1998;129:368᎐371. Kaji H, Oshaki Y, Rocujo C, Higashi T, Fujino A, Kamada T. Determination of blood and urine Mn concentrations and the applications of static sensography as the indices of Mn exposure among Mn refinery workers. Sangyo Ika DaigakuZashi 1993;15:287᎐296. Lonnerdal B. Effects of milk and milk components on Ca, Mg and trace element absorption during infancy. Physiol Rev 1997;77:643᎐669.
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R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
Loranger S, Zayed J. Environmental contamination and human exposure to airborne total and respirable Mn in Montreal. J Air Waste Manag Assoc 1997;47:983᎐989. Mumcu S, Aras NK. Determination of minor and trace element in human diet by AAS. In: Bratter P, Schramel P, editors. Trace element analytical chemistry in medicine and biology. Berlin New York: Walter de Gruyter & Co, 1988:392᎐397. Negi BS, Sadasivan S, Mishra UC. Aerosol composition and sources in urban areas in India. Atmos Environ 1987;21:1259᎐1266. Nielsen FH. Ultratrace Minerals. In: Maurice ES, James AO, Mashe S, editors. Modern nutrition in health and disease. 8th Philadelphia: Lea & Sebiger, 1994:269᎐286. Pirrone N, Keeler GJ. A preliminary assessment of the urban population in the Great Lakes Region. Sci Total Environ 1996;189:91᎐98. Raghunath R, Tripathi RM, Khandekar RN, Nambi KSV. Retention times of Pb, Cd, Cu and Zn in children’s blood. Sci Total Environ 1997;207:133᎐139. Raghunath R, Tripathi RM, Kumar AV, Sathe AP, Khandekar RN, Nambi KSV. Assessment of Pb, Cd, Cu and Zn
exposures of 6᎐10 Y old children in Mumbai. Environ Res 1999;80A:215᎐221. Roels H, Lauwerys R, Genet P. Relationship between external and internal parameters of exposure to Mn in workers from a Mn oxide and salt producing plant. Am J Ind Med 1987a;11:297᎐305. Roels H, Lauwerys R, Buchet JP, Genet P, Sarhan MJ. Epidemiological survey among workers exposed to Mn: effects on lung, CNS and some biological indices. Am J Ind Med 1987b;11:307᎐327. Tripathi RM, Radha R, Krishnamoorthy TM. Dietary intake of heavy metals in Mumbai City India. Sci Total Environ 1997;208:149᎐159. Tripathi RM, Radha R, Sastry VN, Krishnamoorthy TM. Daily intake of heavy metals by infants through milk and milk products. Sci Total Environ 1999;227:229᎐235. Willium WB. Autonomic function in Mn alloy workers. Environ Res 1998;78:52᎐58. Woittiez JRW, Iyengar GV. Trace elements in human clinical specimens. Evaluation of literature data to identify reference values. In: Trace Element Analytical Chemistry in Medicine and Biology 1988;5:229᎐235.
Daily intake of manganese by the adult population of Mumbai R.M. TripathiU , Suchismita Mahapatra, Radha Raghunath, V.N. Sastry, T.M. Krishnamoorthy En¨ ironmental Assessment Di¨ ision, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India Received 14 September 1999; accepted 19 December 1999
Abstract The daily intake of manganese ŽMn. estimated through air, water and duplicate dietary analysis is found to range from 0.67 to 4.99 mg with a mean value of 2.21 mg. Ingestion through food contributed to the predominant fraction of the intake. The turnover rate of Mn through blood is approximately 2 h, based on the mean concentration of Mn in blood of 1.54 g ly1. The average concentrations of Mn in water and air were approximately 1.42 g ly1 and 37 ng my3, respectively. The daily intake of Mn by the adult population of Mumbai is closer to the lower bound of the recommended limit of 2᎐5 mg. Electro Thermal Atomic Absorption Spectrophotometry ŽET-AAS., has been used for the determination of Mn in a variety of environmental and human biological fluids. The detection limit of Mn for a volume injection of 20 l is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities Ž0.5᎐10 ppm. and is found to be within "8%. The reliability of estimation is further assessed through the analysis of Standard Reference Materials ŽSRMs. of soil, hay, milk powder and fish tissue obtained from IAEA. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Mn; Blood; Dietary intake; Ingestion; ET-AAS
1. Introduction Man’s essential requisites of air, water and food contain trace amounts of a wide range of
U
Corresponding author. E-mail address: [email protected] ŽR.M. Tripathi.
heavy metals, some of them have a significant role in several biochemical processes, whereas others are contaminants ŽPirrone and Keeler, 1996; Raghunath et al., 1997; Tripathi et al., 1999.. Manganese is an essential trace element for humans to maintain normal metabolism. Manganese intake through food must be, in general, sufficient to prevent deficiency ŽDonna and
0048-9697r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 0 . 0 0 3 6 0 - 0
44
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
Baldwin, 1997.. The best-defined deficiency symptom observed in animals relate to skeletal abnormalities where the organic matrix of bones and cartilage tend to be poorly developed ŽFardy et al., 1992.. Manganese is subjected to delicate homeostatic control and approximately 3᎐5% of ingested Mn is absorbed and it is rapidly cleared from the blood through the liver. It has been established that the whole blood Mn is a valid indicator of body Mn status and can be used for the diagnosis of diseases when the metabolism of trace element is disrupted ŽGreger, 1998.. At a lower level, manifestations of Mn deficiency occur while high levels of Mn exposure are associated with neurologic and neuropsychiatric disorders ŽDonna, 1999.. Chronic exposure to Mn causes neurophysiological abnormalities ŽKaji et al., 1993.. Thus, the information on the intake levels of Mn is important in assessing the risk to human health. Due to its very low concentrations in a variety of environmental and biological samples such as air, water, food, serum and urine; any analysis requires the use of an accurate analytical method with sufficient sensitivity. The sensitivities offered by methods such as energy dispersive X-ray fluorescence ŽEDXRF., atomic emission spectrometry with inductively coupled plasma excitation ŽAES-ICP. are not sufficient for accurate determination of Mn at concentrations usually encountered in biological samples ŽWillium, 1998; GBC, 1994.. The ET-AAS technique offers the required sensitivity levels and can determine Mn in biological sample matrices in parts per billion levels. The purpose of this study is to standardize a reliable method for the determination of Mn in a variety of environmental materials such as water, air particulate, duplicate diet, blood and urine for estimating its daily intake and turn over rate in the adult population of Mumbai.
2. Experimental 2.1. Sampling locations Samples were collected from different locations in Mumbai viz. Mahim, Bandra, Shivaji park,
Dadar, Anushaktinagar and Vashi during 1998᎐1999. Blood, duplicate diet, urine, drinking water and milk samples were collected from each location from volunteers of middle class families who were not exposed to Mn source. 2.2. Sample collection and processing 2.2.1. Air Air particulate samples were collected for durations of 24 h on Whatman EPM 2000 filter papers at a flow rate of 1000 l miny1 using a high volume sampler. Average flow rate was taken into account for calculation of the volume of the air sampled. Air particulate samples collected on filter papers were wet digested with a mixture of electronic grade nitric acid, hydrochloric acid and perchloric acid. The residue was taken up in 10 ml of 0.25% nitric acid. Filter paper blanks and acid blanks were also taken through the same procedure simultaneously. 2.2.2. Duplicate diet In order to study the dietary intake of Mn by the Mumbai adult population, 60 samples of ‘duplicate diet’ were collected. They were weighed and homogenized in the laboratory. A known weight of sample Ž; 20 g. was dry ashed at a temperature of 400⬚C. The ashed sample was then treated with 1 ml electronic grade nitric acid and the residue was dissolved in 10 ml of 0.25% HNO3 . The details of sample collection and processing are given elsewhere ŽTripathi et al., 1997.. 2.2.3. Blood Blood samples of 1 ml were collected from adults Žwith no occupational Mn exposure. residing in different parts of Mumbai with special care by vein puncture into heparinized pretreated clean polypropylene tubes. Serum samples Ž1 ml. were separated from clotted blood. The blood Žwhole blood. and serum samples were wet digested in duplicate with electronic grade nitric acid and perchloric acid. Digested samples were made up to 2 ml using 0.25% nitric acid. Extreme care was taken to avoid any contamination during sample collection and processing. Reagent blanks were also taken simultaneously using the same proce-
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
dure. The details of sample collection and processing are given elsewhere ŽRaghunath et al., 1999.. Drinking water, milk and urine samples were collected in pretreated polypropylene containers. The details of collection and processing of water, urine and milk are given in our earlier publications ŽRaghunath et al., 1997; Tripathi et al., 1999.. 2.3. Reagents All chemicals used were Merck, Suprapur, Analar or electronic grade. Reagents used for wet ashing were concentrated nitric acid ŽElectronic grade. and perchloric acid ŽSuprapur grade.. Standard stock solution Ž0.01 M. of Mn was prepared and necessary dilutions were made as and when required. 2.3.1. Precautions Quartz, Teflon and high purity polyethylene containers have been used for collection, decomposition and storage of samples prior to analysis. In the present study, all laboratory wares used in sample collection, ashing, analysis and storage were soaked in 10% HNO3 for several days and then rinsed thoroughly with distilled and double distilled water, respectively, before use. Reagent blanks were taken along with each batch of sample and the Mn concentration observed in these blank samples were subtracted from the corresponding batch of field samples. Blank samples always showed extremely low levels of Mn Ž- 4 pg absolute..
45
2.4. Instrumentation A GBC-904 atomic absorption spectrophotometer and GF-3000 automated graphite furnace system were used. The system comprises GF-3000 graphite furnace and PAL-3000 programmable automatic sampler. This combination of equipment is particularly suited for trace analysis since the PAL-3000 can automatically prepare a range of standards from a single stock solution, inject a chemical modifier and even automatically prepare a series of standard additions. A deuterium lamp background corrector was used in all instances. A GBC hollow cathode lamp was used as a light source. The operating conditions are described below: Operating conditions for manganese determination by ETAAS Atomization Analytical line Žnm. Slit width Žnm. Lamp current ŽmA. Absorbance measurement mode Sampling mode Sample injection Calibration method
Furnace 279.5 0.2 9.0 Peak area Auto Sampling Volume 20 l Auto calculated
The furnace conditions were set to give complete drying of the sample without boiling. The ashing temperature of 700⬚C was found to yield the maximum absorbance. The operating graphite furnace program is given in Table 1.
Table 1 Temperature program of graphite furnace Step
Final temp. Ž⬚C.
Ramp time Žs.
Hold time Žs.
Gas type
Read
Signal graphics
1 2 3 4 5 6 7
40 100 120 700 700 2400 2500
10 10 10 10 0.2 1 1
5 10 10 10 1 1 1
None Inert Inert Inert None None Inert
Off Off Off Off Off On Off
Off Off Off Off Off On Off
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
46
3. Results and discussion
Table 2 Concentrations of Mn in standard reference materials
3.1. Interference study
S.N.
Reference material
Unit
Observed value Ž7 replicates.
Certified value
The precision of the procedure was established by analyzing Mn in synthetic samples containing different elements such as Pb, Cd, Cu, Zn, Cr, Co, Ni, In, Tl, Fe, Sn, Ti, Bi, Se and Mg in different quantities Ž0.5᎐10 ppm.. The recovery of Mn was established by determining the added Mn contents in the synthetic samples. The results demonstrate that the recovery of the Mn is quantitative and no interference was observed due to the presence of other elements.
1
Soil-7 IAEA S-7 Hay IAEA V-10 Milk powder IAEA A᎐11 Fish tissue MA-B-3rTM
g gy1
626 Ž624᎐630. 44 Ž42᎐47. 255 Ž252᎐257. 2.57 Ž2.45᎐2.73.
631 Ž604᎐650. 47 Ž32᎐52. 257 Ž248᎐266. 2.62 Ž2.22᎐3.03.
2 3 4
g gy1 ng gy1 g gy1
3.3. Concentrations of Mn in different en¨ ironmental matrices
3.2. Quality assurance The mean concentration of Mn in air particulate, serum, blood, urine, cow milk, human milk, drinking water and duplicate diet samples along with range are given in Table 3. The reported data is based upon a number of measurements.
The reliability of the procedure for estimation of Mn in environmental and biological samples by ET-AAS has been further assessed by analyzing the standard reference materials such as soil-7, milk powder ŽA-11., fish tissue ŽMA-B-3rTM. and hay ŽV-10. obtained from the International Atomic Energy Agency. The results agree within "7% with certified values ŽTable 2.. The validity of the method was further ascertained by crossmethod checks, spike recovery and replicate analysis. The detection limit of Mn for a volume injection of 20 l is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities Ž0.5᎐10 ppm. and is found to be within "8%.
3.4. Mn concentrations in air
The Mn levels in air particulate samples collected from Mumbai were found to vary from 15᎐65 ng my3 with a mean of 37 ng my3 . Negi et al. Ž1987. have reported a value of 46 ng my3 for Mumbai atmosphere. Loranger and Zayed Ž1997. have reported the respirable and total Mn air-
Table 3 Concentrations of Mn in different environmental and biological matrices S.N.
1 2 3 4 5 6 7 8
Matrix
Serum Whole blood Urine Air particulate Cow milk Human milk Drinking water Duplicate diet
No. of samples
Unit
35 60 20 15 30 25 15 60
ng ml y1 ng ml y1 ng ml y1 ng my3 ng ml y1 ng ml y1 ng ml y1 mg d y1
Mn concentration Mean
Min
Max
0.45 1.54 0.3 37 1.13 1.0 1.42 2.21
0.11 0.70 0.15 15 0.37 0.69 1.1 0.67
1.2 4.3 1.9 65 3.2 1.8 2.9 4.99
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
47
borne concentrations at Montreal to be 24 and 50 ng my3 , respectively. 3.5. Mn concentrations in drinking water The levels of Mn in drinking water at Mumbai was found to vary from 1.1 to 2.9 ng mly1 with a mean of 1.42 ng mly1 , which is much lower than the stipulated drinking water standards of 2 ppm by the Bureau of Indian Standards ŽBIS, 1998.. As far as is known, humans suffer no harmful effects from drinking water containing manganese. Levels of Mn become depleted when exposed to the air owing to the oxidation of Mnq2 to Mnq4 state, which eventually precipitates as oxide form. The rates of oxidation are not rapid and thus reduced forms can persist for sometime in aerated waters. This is especially true when the pH is below 9. The rates may be increased by the presence of some inorganic catalysts or through the action of certain microorganisms. 3.6. Mn le¨ els in blood The levels of Mn in serum were found to vary from 0.11 to 1.2 ng mly1 while the same in whole blood varied between 0.7 and 4.3 ng mly1 . The frequency distribution of Mn levels in blood samples is shown in Fig. 1. It is seen from the figure that the maximum percentage Ž40%. of the population have Mn blood levels between 0.75 and Table 4 Mn levels in blood reported in different countries S.N. Country
1 2 3 4 5 6 7
USA
Concentration Reference Žng mly1 .
1.2 Ž0.7᎐2.0. Canada 7.2 Belgium 5.7 Ž0.4᎐13.1. Netherlands 0.63 Ž0.54᎐1.76. Australia 2.0 India 1.54 Ž0.7᎐4.3. Threshold value 10
Willium Ž1998. Donna et al. Ž1994. Roels et al. Ž1987a. Woittiez and Iyengar Ž1988. GBC Ž1994. Present study Ž1999. Roels et al. Ž1987b.
Fig. 1. Frequency distribution of Mn in blood in Mumbai during 1999.
1.25 ng mly1 . For comparison, the concentrations of Mn in blood reported from different countries are given in Table 4. It is evident from the table that the Mn blood levels reported for USA, Netherlands and Australia are comparable to the values observed in the present study. The Mn levels in the blood of the adult population of Mumbai is lower than the threshold level of 10 ng mly1 suggested by Roels et al. Ž1987a,b.. 3.7. Mn le¨ els in urine The mean concentrations of Mn in urine samples were observed as 0.3 ng mly1 in the adult population of Mumbai Žrange s 0.15᎐1.9 ng mly1 . and this is comparable with the value of 0.62 ng mly1 reported for adults in Canada ŽDonna et al., 1994.. Daniel Ž1998. have reported urine Mn levels as 0.2 ng mly1 for residents of the USA. 3.8. Mn in duplicate diet The daily intake depends both on the concentration of Mn in the food materials and the amount consumed. The main food of the Indian population is rice or wheat and hence concentration of Mn in cereals contribute a major part to the total daily intake. The daily consumption of fruits, meat and milk is generally much less compared to cereals and pulses and hence their con-
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50
48
tribution to the total daily intake of Mn is quite low. The Mn concentrations in human milk ranged between 0.69 and 1.8 ng mly1 and this is lower than 4 y 8 ng mly1 reported by Lonnerdal Ž1997. for California. The daily dietary intake of Mn was estimated by ‘duplicate diet’ analysis which was based on the analysis of cumulative food including liquid food Že.g. tea, coffee, milk, water, etc.. consumed during 24 h. The dietary intake of Mn varied between 0.67 and 4.99 mg dayy1 with a mean of 2.21 mg dayy1 . The variations in daily intake of Mn through duplicate diet in different suburbs of Mumbai is given in Table 5. The dietary intake of Mn by the population dwelling in Dadar and Anushaktinagar suburbs was relatively higher compared to that of other areas, however, no specific reason could be attributed to this fact. An attempt was also made to study the Mn dietary intake through vegetarian Ž2.21 mg dayy1 .rnon-vegetarian Ž2.19 mg dayy1 . diet, however, no significant difference was observed during this study. It has been reported ŽFardy et al., 1992; Nielsen, 1994. that the Mn intake through a vegetarian diet is more than that of a non-vegetarian diet since cereals Ž2.48 mg dayy1 ., leafy vegetables Ž0.12 mg dayy1 . and tea Ž690 g dayy1 . are rich in Mn compared to meat Ž0.008 mg dayy1 ., fish Ž0.011 mg dayy1 . and dairy Table 5 Dietary intake of Mn for different areas in Mumbai S.N.
Place
No. of samples
G.M. Žmg dayy1 .
GSD
1 2 3 4 5 6
Mahim Bandra Shivaji park Dadar Anushaktinagar Vashi
14 11 9 6 9 11
2.46 2.09 1.68 3.75 3.91 1.07
1.65 2.11 1.39 1.21 1.26 1.13
Fig. 2. Frequency distribution of dietary intake of Mn by the population of Mumbai.
products Ž0.005 mg dayy1 .. The frequency distribution of Mn levels in duplicate diet samples ŽFig. 2. reflects that the maximum percentage Ž32%. of the population have the dietary intake between 1.5 and 2.25 mg dayy1 . 3.9. Daily total intake through inhalation and ingestion The daily total intake of Mn through inhalation and ingestion of water and food is shown in Table 6. The air borne Mn levels varied between 15 and 65 ng my3 in the atmosphere of Mumbai. The daily intake of Mn contribution through inhalation worked is in the range of 0.3᎐1.3 g Žor 0.004᎐0.018 g kgy1 . based on a 20 m3 air intake for a 70-kg adult. Loranger and Zayed Ž1997. have reported the daily intake of Mn through inhalation as 0.001᎐0.05 g kgy1 for the Canadian population which is slightly higher than that observed during this study.
Table 6 Daily intake of Mn by the Mumbai adult population Source
Daily requirement
Mn concentration
Total daily intake
Absorption fraction Ž%.
Daily uptake Žg.
Air Water Food Total
20 m3 2.0 l ᎐
37 ng my3 1.42 g l y1 2.21 mg dy1
0.74 g 2.84 g 2.21 mg 2.21 mg
50 5 5 ᎐
0.37 0.142 110.5 111.0
R.M. Tripathi et al. r The Science of the Total En¨ ironment 250 (2000) 43᎐50 Table 7 Daily intake of Mn in different countries S.N.
Country
mg dy1
Reference
1 2 3 4 5 6 7
USA Germany Belgium UK Australia India ESADDIa
2.4 2.7 2.6 4.6 2.96 2.23 2᎐5
Mumcu and Aras Ž1988. Mumcu and Aras Ž1988. Buchet and Lauwenys Ž1983. Mumcu and Aras Ž1988. Fardy et al. Ž1992. Present study Ž1999. Greger Ž1998.
a
Estimated safe and adequate daily dietary intake.
The total intake of Mn through the duplicate diet study was 2.21 mg dayy1 which is closer to the lower bound of recommended intake value of 2᎐5 mg dayy1 given by the Food and Nutrition Board ŽFardy et al., 1992.. The intake of Mn via inhalation route is much lower compared to the ingestion pathway. The net uptake of Mn through inhalation and ingestion pathways works out to be 0.111 mg dayy1 . This daily total intake of Mn by the Mumbai adult population is comparable ŽTable 7. with the reported values for some countries like USA, Belgium and Germany, however, it is closer to the lower bound of the Provisional Tolerable Daily Intake Value ŽGreger, 1998.. Tea extract contain high levels of manganese, approximately 2300 g ly1 ŽFardy et al., 1992. and a significant increase of approximately 21᎐45% in the daily intake of manganese for adults could occur when tea contributions are included in the diet. 3.10. Turno¨ er rate of Mn The turnover rate Ž1r . of ingested Mn has been calculated using the single component first order kinetics relating intake and steady concentration of Mn in blood as reported below: dcrdt s fI y CV where, C s concentration of Mn in blood Žg ly1 ., f s fractional uptake Ž5%., I s daily intake of Mn Žmg dayy1 ., V s volume of blood in the body Ž5.2 l. and s elimination rate constant. The turnover rate of ingested Mn in blood under steady state condition works out to be
49
approximately 2 h based on the observed mean concentration of Mn in blood as 1.54 g ly1 and the daily intake of Mn as 2.21 mg.
4. Conclusions The dietary intake of Mn for the Mumbai adult population was found to be 2.21 mg dayy1 , which is within the recommended daily intake. The ingestion pathway was found to be the main route of Mn uptake by adults. The average concentration in the atmosphere of Mumbai was found to be 37 ng my3 . The Mn levels in blood of adult population in Mumbai City was found to be 1.54 ng mly1 , which is lower than the threshold level. The frequency distribution pattern of dietary intake indicates values between 1.5 and 3 mg dayy1 for more than 50% of the study group. References BIS. Packaged natural mineral water ᎏ specifications. Bureau of Indian Standards, 1998;IS:13428. Buchet JP, Lauwenys R. Oral daily intake of Cd, Pb, Mn, Cu, Cr, Hg, Ca, Zn, As in Belgium: a duplicate meal study. Food Chem Toxicol 1983;21:19᎐24. Daniel CP. Trace metals in urine of United States residents: reference range concentrations. Environ Res 1998;76: 53᎐59. Donna M, Huel G, Bowler R, Baldwin M, Robert T, Martin L. Nervous system dysfunction among workers with long term exposure to Mn. Environ Res 1994;64:151᎐180. Donna M, Baldwin M. Early manifestations of Mn neuro toxicity in humans: an update. Environ Res 1997;73:92᎐100. Donna M. Neurotoxic effects of low level exposure to Mn in human populations. Environ Res 1999;80A:99᎐102. Fardy JJ, McOrist GD, Farrar YJ. The determination of Mn status in the Australian diet using neutron activation analysis. J Radioanal Nucl Chem 1992;163:195᎐203. GBC Ž1994.. Graphite furnace methods manual ᎏ application of System FG-2000r3000. GBC Scientific Equipment Pty Ltd, Australia 1994. Greger JL. Dietary standards for Mn: overlap between nutritional and toxicological studies. J Nutr 1998;129:368᎐371. Kaji H, Oshaki Y, Rocujo C, Higashi T, Fujino A, Kamada T. Determination of blood and urine Mn concentrations and the applications of static sensography as the indices of Mn exposure among Mn refinery workers. Sangyo Ika DaigakuZashi 1993;15:287᎐296. Lonnerdal B. Effects of milk and milk components on Ca, Mg and trace element absorption during infancy. Physiol Rev 1997;77:643᎐669.
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Loranger S, Zayed J. Environmental contamination and human exposure to airborne total and respirable Mn in Montreal. J Air Waste Manag Assoc 1997;47:983᎐989. Mumcu S, Aras NK. Determination of minor and trace element in human diet by AAS. In: Bratter P, Schramel P, editors. Trace element analytical chemistry in medicine and biology. Berlin New York: Walter de Gruyter & Co, 1988:392᎐397. Negi BS, Sadasivan S, Mishra UC. Aerosol composition and sources in urban areas in India. Atmos Environ 1987;21:1259᎐1266. Nielsen FH. Ultratrace Minerals. In: Maurice ES, James AO, Mashe S, editors. Modern nutrition in health and disease. 8th Philadelphia: Lea & Sebiger, 1994:269᎐286. Pirrone N, Keeler GJ. A preliminary assessment of the urban population in the Great Lakes Region. Sci Total Environ 1996;189:91᎐98. Raghunath R, Tripathi RM, Khandekar RN, Nambi KSV. Retention times of Pb, Cd, Cu and Zn in children’s blood. Sci Total Environ 1997;207:133᎐139. Raghunath R, Tripathi RM, Kumar AV, Sathe AP, Khandekar RN, Nambi KSV. Assessment of Pb, Cd, Cu and Zn
exposures of 6᎐10 Y old children in Mumbai. Environ Res 1999;80A:215᎐221. Roels H, Lauwerys R, Genet P. Relationship between external and internal parameters of exposure to Mn in workers from a Mn oxide and salt producing plant. Am J Ind Med 1987a;11:297᎐305. Roels H, Lauwerys R, Buchet JP, Genet P, Sarhan MJ. Epidemiological survey among workers exposed to Mn: effects on lung, CNS and some biological indices. Am J Ind Med 1987b;11:307᎐327. Tripathi RM, Radha R, Krishnamoorthy TM. Dietary intake of heavy metals in Mumbai City India. Sci Total Environ 1997;208:149᎐159. Tripathi RM, Radha R, Sastry VN, Krishnamoorthy TM. Daily intake of heavy metals by infants through milk and milk products. Sci Total Environ 1999;227:229᎐235. Willium WB. Autonomic function in Mn alloy workers. Environ Res 1998;78:52᎐58. Woittiez JRW, Iyengar GV. Trace elements in human clinical specimens. Evaluation of literature data to identify reference values. In: Trace Element Analytical Chemistry in Medicine and Biology 1988;5:229᎐235.