Toxicology and Industrial Health http://tih.sagepub.com Mercury vapor inhalation and its effect on glutathione peroxidase in goldsmiths exposed occupationally
K. Jayaprakash Toxicol Ind Health 2009; 25; 463 originally published online Jul 31, 2009; DOI: 10.1177/0748233709106769 The online version of this article can be found at: http://tih.sagepub.com/cgi/content/abstract/25/7/463
Published by: http://www.sagepublications.com Additional services and information for Toxicology and Industrial Health can be found at: Email Alerts: http://tih.sagepub.com/cgi/alerts Subscriptions: http://tih.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.co.uk/journalsPermissions.nav Citations http://tih.sagepub.com/cgi/content/refs/25/7/463
Downloaded from http://tih.sagepub.com at SAGE Publications on November 9, 2009
Mercury vapor inhalation and its effect on glutathione peroxidase in goldsmiths exposed occupationally
K Jayaprakash
Toxicology and Industrial Health 25(7) 463–465 ª The Author(s) 2009 Reprints and permission: http://www. sagepub.co.uk/journalsPermission.nav DOI: 10.1177/0748233709106769 tih.sagepub.com
Abstract In the gold ornaments manufacturing cottage industries, the gold metal grain dust waste particles are recovered from mercury (Hg) amalgam. The results on air samples from these industries during the recovery process have shown a high prevalence of Hg vapor (42.7 mg/m3). The blood concentration of Hg is elevated (79.1 mg/L) among workers when their blood samples are tested. The Hg toxicity is reflected in the reduction of glutathione peroxidase enzyme activity in RBC (49.317 mg/L of RBC) when compared with the data from control subjects (68.536 mg/L of RBC). These values are statistically significant. This would suggest that the Hg poisoning in goldsmiths is due to exposure. The results are discussed with relation to preventive measures. Keywords glutathione peroxidase, gold jewels, Hg toxicology, industrial toxicology, mercury effect
Introduction
Occupational safety is needed to protect laborers from the hazards of different types of toxic chemicals. In recent days, lack of careful handling and disposal practices gives rise to various types of occupational hazards. Occupational health of industrial laborers is under threat (Agnihotram Ramanakumar, 2005). Goldsmiths are known for using potent toxic chemicals such as amyl nitrates (polishing material), ammonium chloride, aniline dyes (stone ink), aqua regia, cadmium, calcium bicarbonate, camphor, copper sulphate, mercury (Hg), nitric acid, potassium alum, potassium cyanide, potassium hydroxide, potassium nitrate, silver nitrate, sulphuric acid, etc. These chemicals are used for melting, refining, welding, electroplating, and polishing the gold metal. Exposure to these substances causes an elevated level of methemoglobin (Jayaprakash, 2003). In the gold ornaments manufacturing cottage industries, the gold metal grain dust waste particles are normally spread on the floor, during the process of making. These gold grain dusts are collected along with other dust particles. They are allowed to settle by sedimentation. The sediment gold is prepared as an amalgam with elemental Hg. The gold amalgam is heated in a crucible with the help of furnace, Hg gets
evaporated, and the melted gold is obtained back. This is one of the traditional crude methods still being practiced by goldsmiths in cottage industries. Hg is toxic on injection or inhalation or skin absorption. Long-term exposure causes damage to the nervous system and kidney. Acute exposure develops nausea, blurred vision, painful breathing, and excessive salivation. Chronic exposure causes memory disturbances, hypertension, and tremors (Clarkson, 1997). Therefore, during the evaporation of Hg in gold ornament-making cottage industries, there is a real chance of Hg vapor posing a health hazard to laborers. In this investigation, an attempt has been made to demonstrate the effects of Hg vapor on goldsmiths.
Materials and methods
The subjects, goldsmiths, in cottage industries exposed to Hg vapor were examined. In identifying
Department of Zoology, Chikkanna Government Arts College, Tirupur, Bharathiar University, Coimbatore, India Corresponding author: K Jayaprakash, Department of Zoology, Chikkanna Government Arts College, Tirupur-641 602 (Affiliated to Bharathiar University, Coimbatore, India), Tamilnadu, India. Email: eswarijp@gmail.com 463
Downloaded from http://tih.sagepub.com at SAGE Publications on November 9, 2009
464 Table 1. Data for the control subjects S.No 1 2 3 4 5 6 7 8 9 10 Hg vapor in air (mg/m3) — — — — — — — — — — Hg in blood (mg/L) — — — — — — — — — — GSH-Px activity (mg/L of RBC) 73.14 66.05 71.11 70.09 61.02 74.15 70.19 66.07 64.22 63.32 S.No 1 2 3 4 5 6 7 8 9 10 Mean
Toxicology and Industrial Health 25(7) Table 2. Data for the experimental subjects Hg vapor Hg in blood in air (mg/L) (mg/m3) 47 59 36 12 41 65 29 44 51 43 42.7 102 74 41 88 69 46 81 117 92 84 79.1 GSH-Px activity (mg/L of RBC) 55.12 58.04 47.11 51.92 59.03 39.17 43.06 57.64 38.05 44.03 49.317 + 8.042 Signs of Hg Toxicity B, H, and T E and H P E and H B P B and P P, K, and M E, H, and P P
Hg, mercury; GSH-Px, glutathione peroxidase. Mean ¼ 68.536 + 4.116.
individuals for the experimental groups, criteria such as age, year of experience, alcohol and cigarette smoking, and eating habits of sea products (as these contribute accumulation of some amount of Hg in tissues) were considered. Individuals who are in similar age and food habits (free from above yardsticks) and working as executive/professionals were selected as matching control subjects. The experimental and control groups were composed of 10 members each. The study was conducted in five different gold cottage industries located in Coimbatore city, India. The working conditions, the area of location, the degree of ventilation, and type of flooring were also taken up for the consideration. The vapor concentration of Hg in the air was measured using palladium chloride (PdCl2)-soaked paper discs. The darkening of the discs due to Hg vapor was estimated with a spectrophotometer. The study was carried out in 2006–2007. The venous blood was collected with the vacutainer polythene (metal free) tubes. The blood samples were analyzed immediately for the concentration of Hg as per the procedure adopted by Tezel, et al. (2001). Citric acid and perchloric acid (5:1) were added. The samples were filtered through Whatman No. 90 mm. The Hg content was determined using a cold vapor atomic absorption kit (Varian 4 S). The mercury analyzer (MA 5800/A, EC India Ltd, Hyderabad62, India) was used for the estimation of Hg. To obtain accuracy, the method was standardized with known amounts of Hg added in control plasma. Every sample was analyzed in triplicate. The unit was given in microgram per liter. The estimation of glutathione peroxidase (GSH-Px) in RBC by spectrophotometry at 412 nm, as outlined
464
by Rotruck, et al. (1973), was followed. All the observed data were analyzed statistically. The Student’s t-test was used for the data of control with that of experimental to ascertain the significance at 95% confidence level (P < 0.05) and to know the influence of Hg poisoning on GSH-Px activity.
Results
The results on air sample tests are given in Tables 1 and 2. From the data, it is evident that an average mean value of 10 different gold cottage industries is recorded as 42.7 mg/m3. A point to be made in this context is that when air has more than 0.25 mg/m3 of Hg, it is indicated as a high-dispersed state. This would suggest the real chance of entry of the Hg vapor in gastrointestinal (GI) tract, skin, and mucous alveolar sac of goldsmiths. The data on plasma concentration of Hg in subjects under investigation are furnished in Table 2. The highest plasma concentration of Hg is recorded as 117 mg/L. The mean value is 79.1 mg/L Hg in plasma. These values are highly significant. The effect of elevated plasma Hg concentration in experimental group reflected in the estimation of GSH-Px. Table 1 is provided with data of GSH-Px in RBC of control subjects. The mean value is 68.536 + 4.12. However, the corresponding mean value of GSH-Px for experimental goldsmiths individual is 49.317 + 8.04. It is inferred from the above data that the Hg toxicity caused a reduction in the
Downloaded from http://tih.sagepub.com at SAGE Publications on November 9, 2009
K Jayaprakash
465
GSH-Px activity. Student’s t table also indicates that these values are statistically significant (Table 2).
Acknowledgements
The author is grateful to the Principal and Prof S Swaminathan, HOD, for their encouragement and the scientist Dr Neelavanan, CECRI, CSIR laboratory Karaikudi, Tamil Nadu for the provision of mercury analyzer.
Discussion
The results of this investigation unambiguously demonstrate a high concentration of Hg in experimental subjects. It has also been established that Hg vapor may easily be absorbed by the GI tract, alveolar sac, and skin. This is evidenced from the data presented in this study. It is known that elemental Hg when it enters into the cellular system destroys sulfhydryl molecules (Clarkson, 1992; Edelson and Cantor, 1998). It is evident from this investigation that GSH-Px is significantly reduced in the experimental group. The biological significance of GSH-Px is to keep the RBC structure intact and prevent cellular wall damage. Glutathione is needed for cells, neuron, and liver (Molin, et al., 1990; Michel, 2003). GSH-Px is reduced considerably due to Hg exposure; it may lead to several ill effects. Therefore, it would be reasonable to assume chronic Hg vapor exposure may cause health abnormalities in goldsmiths. The proper ventilation of the work area and using of nose masks and gloves during the manufacturing process may reduce the risk of Hg vapor toxicity. Proper awareness of the risks in handling the Hg and knowledge of the ill effects of Hg vapor may also be a preventive measure. Further investigations are ongoing to ascertain the Hg toxicity and the biochemical toxic manifestation among these goldsmiths. References
Agnihotram Ramanakumar, V (2005) An overview of occupational health research in India. Ind J Occup Environ Med 9: 10–14. Clarkson, T (1997) The toxicology of mercury. Crit Rev Clin Lab Sci 34: 369–403. Clarkson, TW (1992) Mercury: major issues in environmental health. Environ Health Perspect 100: 31–38. Edelson, SB, Cantor, DS (1998) Autism: xenobiotic influences. Toxicol Ind Health 14: 553–563. Jayaprakash, K (2003) Acquired methaemoglobinemia (Met Hb) in goldsmiths – A hitherto unobserved occupational hazard. Ind J Occup Environ Med 7: 16–18. Michel, G (2003) Cases of mercury exposure, bioavailability and absorption Ecotoxicol Environ Safe 56: 174–179. Molin, M, Bergman, B, Marklunel, SL, Schutz, A, Skerfring, S (1990) The influence of dental amalgam placement on mercury, selenium and glutathione peroxidase in Man. Acta Odontol Scand 48: 287–295. Rotruck, JT, Pope, AL, Ganther, HE, Swanson, AB, Hafeman, DG, Hockstra, WG (1973) Biochemical role of selenium as a component of glutathione peroxidase. Science 179: 588–590. Tezel, H, Ertas, OS, Ozata, F, Erakin, C, Kayalni, A (2001) Blood mercury levels of dental students and dentists at a dental school. Br Dent J 191: 449–459.
465
Downloaded from http://tih.sagepub.com at SAGE Publications on November 9, 2009
