Scalp Hair Mercury Concentrations in Pakistan

2 downloads 0 Views 129KB Size Report
Kagoshima University Graduate School of Medical and Dental Sciences,. 8-35-1 ... of Basic Medical Sciences and 5Department of Clinical Medicine, National.
Research

Environmental Sciences, Vol. 14, No. 4 (2007) 167–175

M. Anwar et al.

ES 658

Scalp Hair Mercury Concentrations in Pakistan Muhammad Anwar*, Tetsuo Ando, Ahmad Maaz1, Sidra Ghani3, Muhammad Munir2, Ihtesham-ud-din Qureshi2, Samina Naeem2, Mayumi Tsuji, Junji Wakamiya4, Atsuhiro Nakano5 and Suminori Akiba Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan 1Department of Community Medicine and 2Department of Pathology, King Edward Medical University, Lahore, Pakistan 3Department of Chemistry, University of Engineering and Technology, Lahore, Pakistan 4Department of Basic Medical Sciences and 5Department of Clinical Medicine, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto 867-0008, Japan (Received October 18, 2006; accepted February 6, 2007) E-mail: [email protected]

*

Key words: PHUFXU\VHOHQLXPKDLUWRHQDLO¿VKFRQVXPSWLRQ3DNLVWDQ

The presence of mercury in the environment is widespread and persistent, but the extent of exposure of Pakistanis to mercury is virtually unknown. We collected toenail and scalp hair samples from 158 subjects (83 males and 75 females) residing in Lahore and its suburbs. We also conducted a questionnaire survey and personal interviews to obtain information on demographic factors, lifestyles, and socioeconomic factors, among others. Mercury concentration in hair samples was measured by cold vapor atomic absorption spectrometry (CVAAS). In addition, the concentration of selenium in the toenail and hair samples was determined by inductively coupled plasma mass spectrometry (ICP-MS). The mean hair mercury concentration was 0.45 SSP &, í DQGGLGQRWVKRZFRUUHODWLRQZLWK¿VKFRQVXPSWLRQDJH area of origin, or present residence. Mercury concentration was higher (p=0.021) in females than in males, and was also higher in subjects with 11 or more years of education (p for trend=0.013). There were 13 subjects with mercury concentration higher than 10 ppm. Most of them were young females and a few were middleDJHG PDOHV :KHQ WKH DQDO\VLV ZDV FRQ¿QHG WR VXEMHFWV ZLWK PHUFXU\ FRQFHQWUDWLRQVORZHUWKDQSSPWKHDPRXQWRI¿VKFRQVXPHGVKRZHGFRUUHODWLRQZLWKKDLU PHUFXU\FRQFHQWUDWLRQZLWKDPDUJLQDOVWDWLVWLFDOVLJQL¿FDQFH S  7KHJHRmetric means of selenium in hair and toenails were 0.87 and 1.01 ppm, respectively. Mercury and selenium concentrations in hair showed no correlation (correlation FRHI¿FLHQW S  7KLVVWXG\VKRZVWKDWPHUFXU\H[SRVXUHOHYHOVDPRQJ residents in Lahore and its suburban areas are relatively low, except among outliers, wherein mercury exposure might be brought about by the use of mercury-containing soaps.

1.

Introduction

Mercury is a naturally occurring heavy metal and is widespread and persistent in the environment.(1) Mercury enters the environment mainly from two sources: QDWXUDOVRXUFHVVXFKDVYROFDQRHVDQGIURPVXUIDFHHPLVVLRQVDQGDUWL¿FLDOVRXUFHV such as from fossil fuel combustion and commercial products. Mercury accumulates

167

Environmental Sciences

Vol. 14, No. 4 (2007) 167–175

M. Anwar et al.

in seawater,(2,3)¿VKWLVVXHDQGDQLPDODQGKXPDQWLVVXHV(4,5) Mercury occurs in the environment in inorganic and organic forms.(6,7) Organic mercury exposure comes PDLQO\IURPHDWLQJ¿VKDQGLQRUJDQLFPHUFXU\H[SRVXUHIURPWKHH[WHUQDOH[SRVXUH to atmosphere containing the breakdown products of mercury-containing pesticides, and fungicides, and dental and mining amalgams.(8) Mercury can permanently damage the human central nervous system, and in more severe cases, affects vital organs such as the lungs and kidneys. The absorpWLRQ RI PHWK\O PHUFXU\ IURP HDWLQJ ¿VK FDQ HQGDQJHU D IHWXV(9) The mammalian nervous system is highly vulnerable to methyl mercury.(10) In general, mercuric compounds bond to the sulfhydryl group of proteins in tissues, membranes, and enzymes resulting in the alteration of their normal functions.(11) Human blood and hair samples have been used for monitoring mercury exposure level in epidemiological studies.(4) Hair is a good choice because of the ease and relative painlessness of sampling, and it offers a more accurate mercury concentration measurement because the mercury concentration of hair is 300 times more than blood.(12) The problem with hair samples is that it is not possible to distinguish methyl mercury accumulation in hair if it is a result of internal or external exposure, and inorganic mercury accumulation in hair results from external exposure.  6HOHQLXPSOD\VDUROHLQWKHPHWDEROLVPRIPHUFXU\LQPDQDQG¿QGLQJVIURP different population groups, such as miners and dentists, suggest the formation of 1:1 +J6HFRPSRXQGVIRUPHUFXU\GHWR[L¿FDWLRQ(13–15) At present, it is believed that the high levels of selenium can protect against the harmful effects of accumulated and retained mercury. The aim of this study was to determine the concentration of mercury in toenail DQGKDLUVDPSOHVDPRQJSHRSOHLQ/DKRUH3DNLVWDQDQGWRLQYHVWLJDWHKRZ¿VKFRQsumption and environmental factors contribute to the mercury exposure level among Pakistanis. We also measured selenium concentration in hair and toenail samples because selenium concentration shows a strong correlation to methyl mercury concentration.

2.

Materials and Methods

2.1 Sample collection Eighty-three males and 75 females who appeared to be healthy were interviewed, and hair and toenail samples were collected from the subjects. All subjects visited Basic Health Units (BHUs) for a health check-up during the period between December 2001 and May 2002. BHU is a medical facility designed to provide a local or regional population with access to primary health care. At present, there are 38 BHUs in the Lahore district and each of them can provide health service for approximately 5,000 to 10,000 people. Through the interviews, we collected information on name, VH[DJHHGXFDWLRQZRUNRFFXSDWLRQSODFHRIELUWKSUHVHQWDGGUHVV¿VKFRQVXPSWLRQ IUHTXHQF\ DQG DPRXQW FRQVXPHG SHU ZHHN RI IRXU PDMRU W\SHV RI ULYHU ¿VK namely, Roho, Sangara, Malee, and Sole), alcohol drinking, and smoking among others. Those with illness or suspected illness seeking medical treatment were excluded from the study. Fourth year medical students of King Edward Medical University under the supervision of faculty members conducted the interviews and samSOLQJGXULQJWKHLU¿HOGWULSVWR%+8V)LIWHHQWRVWXGHQWVDFFRPSDQLHGE\DIHZ faculty members, carried out each visit to the BHUs as part of their medical training. During each visit, approximately 30 to 40 persons underwent health check-up and about 20 of them indicated their willingness to participate in the study. The purpose of the toenail and hair sample collection was explained to each subject using local languages (Punjabi or Urdu), and informed consent was obtained before the start of the study. The Research Ethics Committee of Kagoshima University approved the protocol of the study.

168

Environmental Sciences

Vol. 14, No. 4 (2007) 167–175

M. Anwar et al.

2.2 Mercury concentration measurement Hair samples were washed in mercury-free detergent solution, and then repeatedly rinsed with distilled water and dried at room temperature. All samples were weighed and then analyzed for total mercury concentration by cold vapor atomic absorption spectrometry (CVAAS) after wet digestion of each sample in 2.5 ml of sulfuric acid and a 1 ml mixture of nitric and perchloric acids at 250°C for 20 min.(16) Every reagent used was graded for heavy metal analysis and was purchased from Nakari Tesque, Inc., Kyoto, Japan. The accuracy of the mercury determination was assessed using IAEA-086 (hair) supplied by International Atomic Energy, Cedex, Monaco, as a reference sample for quality control. For each run, two reagent blanks and two reference solutions were analyzed using the same procedure as that for the samples to check the purity of the reagents, and to check for possible contamination. All reagents used in this study were of high-purity analytical grade for trace metal analysis. Glassware was soaked in 5% nitric acid overnight and rinsed with redistilled water before use. Three of the hair samples were alkali-hydrolyzed with 10% KOH solution, and then a portion of the alkali solution was used for the measurement of total mercury concentration. The residual alkali solution was neuWUDOL]HG DQG DFLGL¿HG ZLWK 1+&O DQG WKHQ RUJDQLF PHUFXU\ RI WKH KDLU VDPSOHV ZDV H[WUDFWHG ZLWK FKORURIRUP IURP WKH DFLGL¿HG VROXWLRQ IRU WKH PHDVXUHPHQW RI organic mercury concentration. The total and organic mercury concentrations of the hair samples were analyzed by CVAAS after wet digestion as described above. The total mercury concentration of 21 soap samples was also analyzed by CVAAS after wet digestion as described above. All reagents used in this study were of high-purity analytical grade for trace metal analysis. Glassware was soaked in 5% nitric acid overnight and rinsed with double-distilled water before use.

2.3 Inductively coupled plasma mass spectrometry (ICP-MS) Toenail and hair samples were cleaned with neutral detergent and rinsed with an ample amount of deionized water, then dried at room temperature and wet-digested into each constituent element with 1 ml of pure water and 1 ml of nitric acid by a Microwave-Accelerated Reaction System (MARS), using MDS-2000, CEM, USA. The digested solution was then used for measuring the species of trace elements using the ICP-MS system (Model POEMS 3, Thermo Jarrell-Ash, USA). For atomic absorption spectroscopy of selenium, a multi-element standard solution for calibration was prepared by mixing 8 species of standard solution. An internal standard solution for determining mass weight of selenium was prepared with 4 species of standard solution single element for atomic absorption spectroscopy. The two standard solutions were measured after every 5 samples for quality control. Measurement was performed three times per sample. When the relative standard deviation of the ICPMS measurements exceeded 10%, the measured selenium values were not used for statistical analysis.

2.4 Statistical analysis  )RUVWDWLVWLFDODQDO\VLVZHFDOFXODWHGJHRPHWULFPHDQDQGFRQ¿GHQFHLQWHUval of heavy metal concentrations. We used log-transformed values of mercury and VHOHQLXPLQWKHOLQHDUUHJUHVVLRQGHWHUPLQHGWKHSYDOXHVDQGLGHQWL¿HGWKHGHWHUminants of heavy metal concentrations.

3.

Results

 2QHKXQGUHGDQG¿IW\HLJKWVXEMHFWVSDUWLFLSDWHGLQWKLVVWXG\7KHEDVLFFKDUacteristics of the subjects investigated are shown in Table 1. All the subjects were Muslims and abstained from drinking alcohol, which is forbidden by the Islamic and local laws. Smoking was not common either, because it creates a bad image, par-

169

Environmental Sciences

M. Anwar et al.

Vol. 14, No. 4 (2007) 167–175

Table 1 Characteristics of population investigated.

Total Age (in years) 01–20 21–30 31+ Areas of origin Lahore Others Present residence Lahore Others Education (in years) No education 1–5 years 6–10 years 11+ years Type of work Jobless Farmer Factory worker Others Unknown Smoking Never smoked Ex-smoker Current smoker Fish consumption  ”JZHHN  !JZHHN  !JZHHN Fish consumption frequency  WLPHZHHN  ±WLPHVZHHN  WLPHVZHHN

Male

Female

83 (100%)

75 (100%)

11 (13%) 42 (51%) 30 (36%)

12 (17%) 45 (60%) 18 (23%)

32 (39%) 51 (61%)

33 (44%) 42 (56%)

60 (72%) 23 (28%)

56 (75%) 19 (25%)

3 (4%) 13 (15%) 7 (8%) 60 (72%)

3 (4%) 5 (7%) 5 (7%) 62 (82%)

41 (49%) 1 (1%) 4 (5%) 37 (45%) 0

60 (80%) 0 0 14 (19%) 1 (1%)

64 (77%) 7 (8%) 12 (15%)

73 (97%) 0 2 (3%)

        

     

        

     

ticularly for females, in this society. More than 70% of the subjects examined lived in Lahore, which is an area hosting various industries that include steel, sports, garments, and shoe making. The suburbs of Lahore are less industrialized. There are ULYHUVEXW¿VKLQJLVFDUULHGRXWRQO\RQDYHU\VPDOOVFDOH7KHUHVLGHQWVRI/DKRUH proper and its suburbs did not differ much in terms of demographic characteristics and lifestyles (data not shown). As shown in Table 2, the geometric mean of hair mercury concentrations is 0.45 ppm (95% CI=0.34–0.60). There was no correlation between mercury concentration DQGIUHTXHQF\RUDPRXQWRI¿VKFRQVXPHGDJHDUHDRIRULJLQRUSUHVHQWUHVLGHQFH On the other hand there was a correlation between sex and mercury concentrations (p=0.021); mercury concentration was higher in females (0.64 ppm) than in males (0.33 ppm). Mercury concentration increased with educational level and was highest in those with 11 or more years of education (p for trend = 0.013). There were 13 subjects with mercury concentration higher than 10 ppm (nine females and four males). Most of them were young females approximately 20 years of age and a few were middle-aged males. These cases are listed in Table 3. All female outliers had 11 or more years of education. The total and methyl mercury concentrations of three of the seven hair samples in which total mercury concentrations

170

Environmental Sciences

M. Anwar et al.

Vol. 14, No. 4 (2007) 167–175

Table 2 Mercury concentrations and demographic factors. N Total Sex Female Male p-value for sex difference Age (in years) 1–20 21– 31+ p-value for trend Area of origin Lahore Others p-value for area difference Present residence Lahore Others p-value for area difference Education (in years) No education 1–5 years 6–10 years 11+ years p-value for trend

95% CI

mean* ppm

158

0.45

0.34–0.60

75 83

0.64 0.33

0.40–1.03 0.23–0.46 0.021

23 87 48

0.50 0.42 0.49

0.19–1.31 0.29–0.61 0.29–0.82 0.913

65 93

0.38 0.50

0.26–0.57 0.33–0.76 0.365

116 42

0.40 0.60

0.29–0.56 0.31–1.15 0.240

6 18 12 122

0.26 0.18 0.27 0.55

0.10–0.68 0.14–0.23 0.13–0.58 0.39–0.79 0.013

geometric mean p-value is obtained by univariate linear regression analysis.

*

Table 3 0HUFXU\DQGVHOHQLXPFRQFHQWUDWLRQVVH[DJHSUHVHQWUHVLGHQFH¿VKFRQVXPSWLRQ DPRXQW  and use of hair dye and skin soap of outliers. Subject 157 136 133 98 43 45 86 146 48 83 71 57 20

Hg (ppm) 16.56 24.31 24.53 24.58 28.80 32.30 40.22 41.40 49.05 90.33 268.45 624.43 1254.54

Se (ppm)

Sex

Age (years)

0.82 0.68 4.12 0.89 0.65 0.66 0.63 0.66 0.86 0.75 0.72 0.72 4.52

F F F F M M F F M F F M F

49 22 18 24 60 45 22 21 27 21 22 52 19

Present Fish consumption Hair Skin soap residence per week (g) dye use use Lahore Lahore F. Abad Sialkot Multan Lahore Lahore Sialkot Lahore Lahore Lahore Jehlam Lahore

20–50 20–50 50–100 100–200 200+ 50–100 200+ 50–100 50–100 20–50 50–100 50–100 0

Yes No Yes No Yes No No No No No No Yes No

Yes Yes Yes Yes No No Yes No No Yes Yes Yes Yes

All subjects had 11 or more years of education.

exceeded 40 ppm were reanalyzed (Table 4). The concentrations of methyl mercury varied from 4.4 ppm to 26.6 ppm, and about four percent of the total mercury concentrations was due to methyl mercury in each of the three reanalyzed samples. The percentage of methyl mercury present was similar among the samples. Furthermore,

171

Environmental Sciences

M. Anwar et al.

Vol. 14, No. 4 (2007) 167–175

Table 4 Reanalysis of hair mercury. 6XEMHFW

20 83 146

7+JFRQFHQWUDWLRQ (ppm) 1st

2nd

1250 90 42

640 126 105

2UJ+J  

26.6 5.0 5.0

2UJ+J7+J

4.2 4.0 4.2

&RHI¿FLHQWYDULDQFH  THg: total mercury Org. Hg: organic mercury

WKHUHZDVDODUJHGLIIHUHQFHEHWZHHQWKH¿UVWDQGVHFRQGDQDO\VHVUHVXOWVVXJJHVWLQJ that mercury adhesion to the samples might not be homogeneous.  :KHQ WKH DQDO\VLV ZDV FRQ¿QHG WR VXEMHFWV ZLWK PHUFXU\ FRQFHQWUDWLRQV ORZHU WKDQSSP WKHXSSHUOLPLWRI&,RI+JFRQFHQWUDWLRQV WKHDPRXQWRI¿VK FRQVXPHGFRUUHODWHGWRKDLUPHUFXU\FRQFHQWUDWLRQZLWKDPDUJLQDOVWDWLVWLFDOVLJQL¿cance (p=0.065), as shown in Table 5. Sex, age, educational level, area of origin, or present residence did not show correlation to hair mercury concentration. The geometric means of selenium in hair and toenails in this study were 0.87 (95% CI=0.79–0.97) and 1.01 ppm (95% CI=0.96–1.07), respectively, and neither was VLJQL¿FDQWO\FRUUHODWHGWRVH[DJHDUHDRIRULJLQSUHVHQWUHVLGHQFHRUHGXFDWLRQDO level (data not shown). Mercury and selenium concentrations of the hair samples did not show correlation (Fig. 1). Selenium concentrations did not show any correlation ZLWK¿VKFRQVXPSWLRQ

4.

Discussion

In this study, the mean hair mercury concentration of 0.45 ppm did not show FRUUHODWLRQZLWKWKHIUHTXHQF\RUDPRXQWRI¿VKFRQVXPHG:KHQWKHDQDO\VLVZDV restricted to subjects with mercury concentrations lower than 0.6 ppm, the amount RI¿VKFRQVXPHGVKRZHGDZHDNFRUUHODWLRQZLWKKDLUPHUFXU\FRQFHQWUDWLRQ7KHUH were 13 outliers with mercury concentration higher than 10 ppm. Most of them were young females and a few were middle-aged males. Among these subjects, no obvious adverse effects of high mercury concentration on their health were observed during the interview. Their present and past medical histories from the questionnaire survey did not indicate any health problems, suggesting external mercury contaminaWLRQUDWKHUWKDQLQWHUQDOFRQWDPLQDWLRQ$OWKRXJK¿VKLVFRQVLGHUHGWREHDQLQWHUQDO source of methyl mercury, the subjects in our study area do not generally eat much ¿VK We tried to reanalyze total and methyl mercury concentrations of the seven hair samples, with total mercury concentration exceeding 40 ppm. Because of the lack of specimens, reanalysis was successful only for three subjects (Table 4). The low percentage of methyl mercury in the total mercury concentration of the three outliers (4.2%) suggests the possibility of a nondietary source of mercury. Because the percentage of methyl mercury to the total mercury is similar in these samples, not only methyl mercury but also inorganic (total except for methyl) mercury is expected to KDYHFRPHIURPVLPLODUVRXUFHV)XUWKHUPRUHDODUJHGLIIHUHQFHEHWZHHQWKH¿UVW and second analyses of the total mercury concentrations suggests that mercury adhesion to hair tends to be heterogeneous. Taken together, these higher concentrations might be due to the external adhesion of mercury to hair. Mercury soaps and similar types of skin creams, which are used for skin whitening, could be possible sources of external mercury exposure. In this study, most of

172

Environmental Sciences

Vol. 14, No. 4 (2007) 167–175

M. Anwar et al.

Table 5 0HUFXU\FRQFHQWUDWLRQLQKDLUDFFRUGLQJWR¿VKFRQVXPSWLRQ +JSSP  N

mean* (ppm)

95% CI

)UHTXHQF\RI¿VKFRQVXPSWLRQ  WLPHZHHN  ±WLPHVZHHN  RUPRUHWLPHVZHHN

  

   p-for trend1

± ± ± 0.274

$PRXQWRI¿VKFRQVXPHG Up to 50 gm 50–100 gm >100 gm

24 45 44

0.16 0.17 0.20 p-for trend1

0.13–0.20 0.14–0.21 0.17–0.24 0.065

* 1

geometric mean p value is obtained by univariate linear regression analysis.

Log Hair Hg

Log Hair Se Outliers

Fig. 1

Scatter diagram of hair mercury and selenium concentrations.

the subjects with abnormally higher mercury concentrations were females, who are known to use skin-whitening soaps and creams with high frequency in Pakistan. Eight out of nine outlier females used skin soaps. We collected 21 different kinds of soap from Pakistani markets for mercury concentration analysis. Only two pieces of the collected soaps contained mercury below the detectable level; however, 10 pieces of the collected soaps had a mercury concentration of more than 10 ppb (Table 6). Because most of the soaps collected were commonly used for washing the face, bathing and washing clothes, a small amount of mercury in these soaps would stain the hair. High mercury concentrations have been associated with the habitual use of toilet and antiseptic soaps, particularly in Africa,(17) and the same trend occurs in Asian countries where people, particularly females, strongly wish to have paler faces. The skin-whitening practice is much more intense in areas with more inter-

173

Environmental Sciences

M. Anwar et al.

Vol. 14, No. 4 (2007) 167–175

Table 6 Mercury (Hg) concentration in commonly used soaps in Pakistan. Soap mercury concentration (ppb)

n

156.9 135.7 20.6–29.5 12.9–17.4 1.40–9.6 Not detected

1 1 5 3 8 2 21

Total GM (ppb) 95% CI

6.142 2.01–18.73

action between Blacks and Whites,(7) and there were integrated populations in our study area. These soaps and creams are locally prepared, without proper monitoring IURPWKHJRYHUQPHQW,QWKHFLWLHVDQGSDUWLFXODUO\WKHYLOODJHVRQHPD\¿QGPDQ\ +DNLPVDQGQRQTXDOL¿HGSK\VLFLDQVVHOOLQJWKHVHSURGXFWVPDNLQJWKHPHDVLO\DFcessible.  )LVK LV D PDMRU VRXUFH RI PHWK\O PHUFXU\  7KH FRUUHODWLRQ EHWZHHQ ¿VK FRQsumption and mercury concentration has been reported in a number of publications.(18,19–22) Fishing and other human activities in the Ravi River and the Lahore Canal can result in accidental exposure because most domestic and industrial wastes are discarded into them without any monitoring by government or private agencies. Subjects working in local industries with no health hazard check can result in ocFXSDWLRQDOH[SRVXUHLQWKHVWXG\DUHD:HIRXQGDPDUJLQDOO\VLJQL¿FDQWFRUUHODWLRQ EHWZHHQ¿VKFRQVXPSWLRQDQGPHUFXU\FRQFHQWUDWLRQRQO\ZKHQZHFRQGXFWHGWKH analysis up to concentrations under 0.6 ppm. However, selenium concentrations did QRW VKRZ FRUUHODWLRQ ZLWK PHUFXU\ FRQFHQWUDWLRQV RU ¿VK FRQVXPSWLRQ VXJJHVWLQJ WKDWWKHPDMRUVRXUFHRIVHOHQLXPLVQRW¿VK,QVRPHFRXQWULHVEHDQVDQGULFHDUH the major sources of selenium.(23) The use of pesticides has dramatically increased in the past decades, particularly in developing countries including Pakistan because agriculture is one of the major pillars of its economy. Agricultural Pesticides Ordinance (APO) was promulgated in 1971 to regulate the import, manufacture, formulation, sale, distribution, use and advertisement of pesticides. The Ministry of Food, Agriculture and Cooperatives, Government of Pakistan, is responsible for its implementation; however, no regular agency for monitoring the implementation of the rules exists.(24) The farmers have inadequate knowledge of pesticides as to their suitability, application techniques and safety measures. This is one of the reasons for the poor pest control, environmental pollution and health problems in some areas. During the rainy season, water from ULYHUVRFFDVLRQDOO\RYHUÀRZVDQGPL[HVZLWKLUULJDWHGZDWHU

5.

Conclusions

This study showed that mercury exposure levels among residents of Lahore and its suburban areas are relatively low, except among outliers, wherein a higher mercury concentration might be caused by contamination with mercury contained in soaps or mercury pesticides.

174

Environmental Sciences

Vol. 14, No. 4 (2007) 167–175

M. Anwar et al.

References 1 Agency for Toxic Substances and Disease Registry (ATSDR) (1999): National Research Council (NRC) 2000. 2 Gardener, D. (1975): Observations on the distribution of dissolved mercury in the ocean. Poll. Bull. 6: 43–46. 3 Slemr, F., Heinz, G.H., Camardese, M.B., Hill, E.F., Moore, J.F. and Murry, H.C. (1981): Latitudinal distribution of mercury over the Atlantic Ocean. J. Geophys. Res. 86: 1159– 1166. 4 Friberg, L. and Nordberg, G.F. (1972): Inorganic Mercury, Relation between Exposure and Effects. Chemical Rubber Company Press, Ohio., pp. 113–139.   *DUGHQHU'  0HUFXU\LQZDWHUVDQG¿VKRIWKH,ULVK6HDDQGRWKHU8.¿VKLQJ grounds. Nature London. 272: 49–51. 6 Horton, J.H., Dorset, R.S. and Cooper, R.E. (1977): Trace metals in the terrestrial HQYLURQPHQWRIDFRDO¿UHGSRZHUSODQW (3$,$*'%  7 Airey, D. and Jones, P.D. (1982): Mercury in the River Mersey, its estuary and tributaries during 1973 and 1974. Water Res. 16: 565–577. 8 Clarkson, T.W.(1977): Mercury poisoning. In: Brown S.S. Eds.: Clinical Chemistry and Chemical Toxicology of Metals. Elsevier, Amsterdam. pp. 189–200. 9 Amin-Zaki, L., Elhassani, S., Majeed, M.A., Clarkson, T.W., Doherty, R.A. and Greenwood, M.R. (1974): Studies of infants postnatally exposed to methyl mercury. J. Pediatr. 85: 81–84. 10 Castoldi, A.F., Coccini, T., Ceccatelli, S. and Manzo, L. (2001): Neurotoxicity and molecular effects of methyl mercury. Brain Res. Bull. 15: 197–203. 11 Aronow, S.P., Aronow, H.D., Blanchard, T., Czinn, S. and Chelimsky, G. (2003): Hair relaxers: a benign caustic ingestion? J. Pediatr. Gastroenterol. Nutr. 36: 120–125. 12 Phelps, R.W., Clarkson, T.W., Kershaw, T.G. and Wheatley, B. (1980): Interrelationships of blood and hair mercury concentrations in a North American population exposed to methyl mercury. Arch. Environ. Health. 35: 161–168. 13 Kosta, L., Byrne, A.R. and Zelenko, V. (1972): Correlation between selenium and mercury in man following exposure to inorganic mercury. Nature. 254: 238–239. 14 Byrne, A.R. and Kosta, L. (1974): Simultaneous neutron-activation determination of selenium and mercury in biological samples by volatilization. Talanta. 21: 1083–1090. 15 Falnoga, I., Tusek-Znidaric, M., Horvat, M. and Stegnar, P. (2000): Mercury, selenium, and cadmium in human autopsy samples from Idrija residents and mercury mine workers. Environ. Res. 84: 211–218. 16 Akagi, H. and Nishimura, H. (1991): Speciation of mercury in the environment. In: Suzuki, T., Imura, N. and Clarkson, T.W. Eds.: Advances in Mercury Toxicology. Plenum Press, N.Y., pp. 53–76. 17 Harada, M., Nakachi, S., Tasaka, K., Sakashita, S., Muta, K., Yanagida, K., Doi, R., Kizaki, T. and Ohno, H. (2001): Wide use of skin-lightening soap may cause mercury poisoning in Kenya. Sci. Total Environ. 269: 183–187. 18 Nakagawa, R. (1995): Concentration of mercury in hair of Japanese people. Chemosphere. 30: 127–133. 19 Hansen, J.C., Kromann, N., Wulf, H.C. and Alboge, K. (1984): Selenium and its interrelation with mercury in whole blood and hair in an East Greenlandic population. Sci. Total Environ. 38: 33–40. 20 Sherlock, J.C., Lindsay, D.G., Hislop, J.E., Evans, W.H. and Collier, T.R. (1982): 'XSOLFDWLRQ GLHW VWXG\ RQ PHUFXU\ LQWDNH E\ ¿VK FRQVXPHUV LQ WKH 8QLWHG .LQJGRP Arch. Environ. Health. 37: 271–278.  %RLVFKLR $$ DQG +HQVKHO '   )LVK FRQVXPSWLRQ ¿VK ORUH DQG PHUFXU\ pollution-risk communication for the Madeira River people. Environ. Res. 84: 108–126. 22 Oskarsson, A., Ohlin, B., Ohlander, E.M. and Albanus, L. (1990): Mercury levels in hair IURPSHRSOHHDWLQJODUJHTXDQWLWLHVRI6ZHGLVKIUHVKZDWHU¿VKFood Addit. Contam. 7: 555–562. 23 Ganapathy, S. and Dhanda, R. (1976): Selenium content of omnivorous and vegetarian diets. Fed. Proc. 35: 360.

175