Mercury exposure and health effects in occupational workers, dental amalgam and whitening creams users

Abstract

Mercury (Hg) is a serious environmental pollutant with various recorded nervous system and developmental effects. Despite its hazardous effects, the Hg is continuously used in various products and processes worldwide due to its unique characteristics. Over hundreds of years Hg has widely been used in industry, gold mining, agriculture, cosmetics, dental amalgam and medicine. The recent discoveries on the toxicity of Hg have unfortunately been ignored for long time, the worst effect of which were more pronounced among workers involved in industries. Human exposed to Hg through various pathways among which the selected areas under study was the fluorescent lamp industry, gold mining, dental amalgam and whitening creams. Therefore the study aimed to identify the Hg concentration in the biological samples (blood, urine, hair, nails) of the Hg exposed occupational workers involved in the fluorescent lamp industry and gold mining processes, in addition the Hg was also identified among the blood, urine hair and nails samples of the dental amalgam and whitening cream users other than occupational workers. The first part of the study is concerned with the exposed occupational workers in the fluorescent lamp industry of Khyber Pakhtunkhwa. This study was conducted to investigate the concentrations of organic (methyl) mercury (Me-Hg), inorganic mercury (I-Hg) and total mercury (T-Hg) in the exposed workers of fluorescent lamp industries. For this purpose biological samples such as red blood cells (RBCs), plasma, urine, hair and nails were collected from Hg exposed workers and non-worker as control group. These samples were analyzed for Hg concentrations and their correlations with the demographic profile of specimen donating persons were assessed. The mean concentrations of T- Hg (31.9 μg/L), Me-Hg (27.7 μg/L) and I-Hg (5.36 μg/L) in RBCs were significantly (P<0.001) higher in exposed workers (n=40) as compared to the control, whereas T- Hg, Me-Hg and I-Hg concentrations in plasma were observed 15.1, 3.5 and 10.6 μg/L, respectively and significantly higher (P<0.001) than the control group. The mean concentrations of T- Hg (137.5 μg/L), Me-Hg (13.5 μg/L) and I-Hg (137.5 μg/L) in urine were also significantly (P<0.001) higher than the control group which were 2.81, 0.31 and 2.38 μg/L, respectively. The concentrations of Hg species (T- Hg, Me-Hg, and I-Hg) were significantly higher in the samples of hair and nail of the workers as compared to the control group. This study concluded that the workers in fluorescent lamp industries were highly exposed to Hg as indicated by the concentrations of Hg and its species in the biological specimen. Numerous health problems were noticed during questionnaire survey which could be linked with high exposure of Hg; therefore, precautionary measures should be adopted such as protective cloths, masks and minimum exposure time by the workers to minimize the health risks. The second part of the study is concerned with the individuals with no occupational exposure to Hg. This part of the study is related with the exposure of individuals to Hg through the use of Hg dental filling for their teeth. The study was conducted among the individuals using Hg as dental filling material to investigate the Hg concentration and its distribution with time (days) in the biological samples of Hg dental amalgam users (MDA). Hg concentration was measured in the biological samples (red blood cells (RBCs), plasma, urine, hair, nails) collected from MDA at three different times (e.g. 1st, 3rd, 12th day) of Hg filling and correlated them with the biological variables (age, weight, restoration, Hg amalgam filling, surface area of filling material, fish consumption). Hg concentrations in the biological samples of MDA were 6-8 times higher than non amalgam users (control). The concentrations of Hg in the RBCs (4.39 μg/L), plasma (3.02 μg/L) and urine (22.5 μg/L) on 1st day of Hg filling was found higher than the concentrations observed on 3rd (2.15, 1.46, 12.3 μg/L for RBCs, plasma, urine, respectively) and 12th (3.05, 2.5, 9.12 μg/L for RBCs, plasma, urine, respectively) day of Hg filling, while in the case of hair and nails, the Hg concentration observed lower on 3rd day (1.53 μg/g for hair) (2.35 μg/g for nails) than 12th day (2.95 μg/g for hair) (3.5 μg/g for nails) of Hg filling. The correlation of Hg concentrations with biological variables indicated that the number of restoration, dental filling, surface area and fish consumption were significantly (p ˂ 0.05) correlated with Hg amalgam filling while non significant (p ˃ 0.05) correlation was observed for the age and weight of MDA. Another serious health problem in which the workers exposed to toxic Hg metal is the use of Hg in gold extraction process because they exposed directly through the inhalation and skin contact. Goldsmith involved in the gold extraction and recovery processes are at high risk of health because Hg is a highly toxic metal. The aim of this work was to determine the concentrations of T-Hg, Me-Hg and I-Hg in the biological samples (plasma, RBCs, urine, hair and nails) of the exposed goldsmith workers named nayaragar in local language. Biological samples (RBCs, urine, hair and nails) were collected from goldsmith (n=40) and analyzed for selected Hg using atomic absorption spectrometer (AAS) equipped with mercury hydride system (MHS). The mean T-Hg concentration in RBCs (33 μg/L), plasma (11.8±3.2 μg/L), urine (168.6±29 μg/L), hair (4.21±0.9 μg/g) and nails (5.91±1.4 μg/g) observed higher than control RBCs (1.64±0.88 μg/L), plasma (0.55±0.27 μg/L), urine (2.72±1.1 μg/L), hair (0.35±0.22 μg/g) and nails (0.51±0.21 μg/g). All the workers participated in this study were suffered from physical and mental diseases. The concentration of Hg was found higher among the workers suffered from mental diseases as compared to those suffered from physical diseases. Among the physical diseases the most serious diseases were included the sexual dysfunction, skin diseases and fatigue because the workers suffered from these diseases have high concentration of Hg than the workers with other diseases. The number of workers suffered from physical diseases (88%) was greater than mental diseases (53%). Among the physical diseases the highest number of workers suffered from chest problem (47%) while 63% from dementia among the mental diseases. The correlation of physical and mental diseases with experience and exposure time showed significant correlation (p ˂ 0.05). The burning process of Hg gold amalgamation is a significant source of Hg exposure to goldsmith nayaragar workers and nearby population, therefore awareness and precautionary measures are necessary and the workers should carry out their work outside the residential area. Another alarming issue found for the common people is the use of Hg in creams and cosmetics. This is the unnecessary exposure of the body to toxic Hg metal. Asians are highly vulnerable to the I-Hg through the use of skin whitening creams. The aim of this work was the quantification of Hg in the skin whitening creams and in the biological samples of whitening cream users (WCU). The Hg concentration observed in the whitening creams was found higher than the permissible limit (1μg/g) set by the US FDA .Similarly when the Hg concentration in the biological samples of these WCU was analyzed, the T-Hg concentration was found significantly (p ˃ 0.05) higher in the plasma (3.61 μg/L), RBCs (9.83 μg/L), urine (21.2 μg/L), nails (1.76 μg/g) and hair (1.23 μg/g) samples of WCU than control plasma (0.57 μg/L), RBCs (1.77 μg/L), urine (3.04 μg/L), nails (0.45 μg/g), hair (0.37 μg/g). Similarly the Me-Hg and I-Hg concentration found in the biological samples was found significantly (p ˃ 0.05) higher than control. Among the whitening creams, Stillmans and White Face creams have comparatively the highest Hg concentration of 63.3 μg/g and 57.6 μg/g respectively. The Hg concentration in the biological samples of the Stillmans and White Face users were comparatively higher than other creams users. It was observed from the study that the use of whitening creams containing Hg is a health hazard and the people especially women should encourage not to use these creams due to the high concentration of Hg. The people should enforce the health sector of Pakistan to regulate this sector and increase awareness about the use of Hg in cosmetics and its hazardous effects.