production of blue colored ceramic in glaze industry is of important concern for structuring of floors and walls .
this is because cobalt has mobile 3d electrons in its atomic structure ( 1 ) .
the main component , such as silica , present in ceramic are similar to glass , causing both favorite melting point and color ( 2 , 3 ) .
this solution then is applied to a clay body at increasing temperature up to 1300c .
therefore , an interface layer is made up by glaze and clay body interaction , then , glaze is adhered to the clay ( 2 , 3 ) .
finally , color is occurred on glaze in result of high temperature reaction . in such process
, cobalt toxicity is taken place when glazers are exposed to the cobalt in powder form . to prevent adverse effect of cobalt , such as , gamut of respiratory disorders , asthma , and also lung cancer , occupational exposures are of great concern in the ceramic industries ( 2 , 3 ) .
cobalt is not a cumulative toxicant and is mainly excreted in urine to a lesser extent via faces .
the two main target organs are the skin and the respiratory tract ( 4 ) .
cobalt is the critical toxic component causing hard metal lung disease ( 5 ) that is a rare form of occupational lung disease that can occur in workers engaged in the manufacture , utilization , or maintenance of tools hard metal .
cobalt may cause allergic dermatitis ( 69 ) , cardiomyopathy ( 10 , 11 ) and asthma ( 7,1215 ) .
exposure to cobalt leads to severe alterations in capillaries , edema and hemorrhage of lung in experimental animals ( 16 ) . in hard metal industries such as cobalt , occupational asthma
the international agency for research on cancer ( iarc ) recently has classified cobalt and cobalt compounds as possibly carcinogenic to humans ( class 2b ) ( 17 ) .
the objectives of this study were to determine the cobalt level in urine of glazers of a ceramic industry and also to find out whether a relationship exists between factors including duration of exposure , work shift breathing masks , skin dermatitis , overtime work , ventilation , age , weight , height , and the urinary concentration of cobalt .
investigation of the relation between occupational exposure in glazers and the lung function was another aim of this study .
mean - while , considerable procedures have been developed for preparing various samples before analysis [ 1819 ] .
solid phase extraction developed in our previous study was used to prepare samples [ 2025 ] followed by inductively coupled plasma - atomic emission spectroscopy ( icp - aes ) .
this case - control study was carried out in glazing units of a ceramic industry where blue - colored ceramic glazes were produced .
a control group consisting of 55 office workers was considered for comparison study . in glazers ,
age ranged from 22 to 50 years with a mean value of 30.67 years and for the control group it was 23 to 50 years with a mean value of 32.6 years .
all participants filled out a self administered questionnaire comprises questions about overtime work , duration of exposure , work shift , use of mask , skin allergy , ventilation , age , weight , and height .
there were not significant differences between glazers who exposed to cobalt and the referents concerning age , weight , and height .
urine samples were taken for determination of cobalt , at the start and end of the work ( totally 98 samples ) .
samples were collected before starting to work and at the end of the work shift while workers removed their work uniforms .
they were advised to wash their hands before sampling in order to reduce the potential for contamination .
twenty milliliters urine was collected in acid - washed polyethylene containers and was stored at + 4c until the analyses time .
cartridges were filled up with 500 mg amberlite xad-7 resin . in order to remove organic and inorganic contaminants , amberlite
2.5 ml urine sample was adjusted at ph 9 and the cobalt present in the samples was chelated with ammonium pyrrolidine dithiocarbamate ( apdc ) .
the solution was then passed through the sorbent at a flow rate of 5 ml / min under gravity .
then , the retained analyte was eluted by 15 ml of 2 m hno 

 3 

 .
the urinary cobalt was analyzed by inductively coupled plasma - atomic emission spectroscopy ( icp - aes ) ( spectro , arcos , germany ) .
the calibration of the icp - aes was performed using standard solutions containing 2001000 g / l of cobalt .
the lung function tests were performed on each control and cobalt exposed subject by spirometer system ( model 2120 ) .
the spirometer was calibrated daily with one liter calibration syringe and operated at temperature ranged from 20 to 25c .
is measurement , forced vital capacity ( fvc ) , forced expiratory volume in one second ( fev1 ) , forced expiratory flow fef 

 2575 

 were measured .
paired t - tests were used to assess the changes between pre- and post - shift measurements for the glazers .
analysis of covariance ( ancova ) was used to evaluate the effect of each factor on post - shift measurement after controlling for the pre - shift shift .
cartridges were filled up with 500 mg amberlite xad-7 resin . in order to remove organic and inorganic contaminants , amberlite
2.5 ml urine sample was adjusted at ph 9 and the cobalt present in the samples was chelated with ammonium pyrrolidine dithiocarbamate ( apdc ) .
the solution was then passed through the sorbent at a flow rate of 5 ml / min under gravity .
then , the retained analyte was eluted by 15 ml of 2 m hno 

 3 

 .
cartridges were filled up with 500 mg amberlite xad-7 resin . in order to remove organic and inorganic contaminants , amberlite
2.5 ml urine sample was adjusted at ph 9 and the cobalt present in the samples was chelated with ammonium pyrrolidine dithiocarbamate ( apdc ) .
the solution was then passed through the sorbent at a flow rate of 5 ml / min under gravity .
then , the retained analyte was eluted by 15 ml of 2 m hno 

 3 

 .
the urinary cobalt was analyzed by inductively coupled plasma - atomic emission spectroscopy ( icp - aes ) ( spectro , arcos , germany ) .
the calibration of the icp - aes was performed using standard solutions containing 2001000 g / l of cobalt .
the lung function tests were performed on each control and cobalt exposed subject by spirometer system ( model 2120 ) .
the spirometer was calibrated daily with one liter calibration syringe and operated at temperature ranged from 20 to 25c .
through is measurement , forced vital capacity ( fvc ) , forced expiratory volume in one second ( fev1 ) , forced expiratory flow fef 

 2575 

 were measured .
paired t - tests were used to assess the changes between pre- and post - shift measurements for the glazers .
analysis of covariance ( ancova ) was used to evaluate the effect of each factor on post - shift measurement after controlling for the pre - shift shift .
important demographic characteristics and the results of the lung function tests for glazers and their matched controls are shown in table 1 .
mean value for age , height , and weight was not significantly different between groups .
mean values of fvc , fev1 , fev1/fvc , and fef 

 2575 

 were lower in the exposed group compared to the control group ( table 1 ) .
analysis of the lung function tests revealed significant differences in all spirometric parameters between the glazers and the control groups ( p<0.001 ) ( table 1 ) .
population characteristics of the study groups urinary level of cobalt at the start of the work shift was ranged from 0.01 to 5 g / l , with a mean value of 1.73 g / l and at the end of the work shift ranged from 0.01 to 15 g / l , with a mean value of 3.47
a significant difference was found between co concentration of start and the end shift samples . there were significant differences in the mean concentration of cobalt between the exposure group and the control group ( table 2 ) .
table 3 gives the results of biological monitoring at the start and end of the work shift .
comparison of urinary cobalt between pre- and post - shift samples in the glazers and control group urinary cobalt measured at pre- and post - shift of the glazers in meybood city of iran the glazers were subdivided in several subgroups according to the variables .
concentrations of co in urine increased during the shift . on the other hand , the highest values of cobalt
based on the work history , there were no significant differences in the mean values of urine cobalt levels between glazers , however , glazers with long work history ( 61month ) had a higher urine cobalt level compared to those who had work history of 24 months ( 4.47 g / l versus 2.14 g / l ) ( table 3 ) .
glazers who were working in the evening had higher urine cobalt compare to the morning shift ( 3.87g / l versus 3.08g / l ) .
ancova showed that , after adjusting for pre - shift cobalt , the effect of shift on post - shift lead was not significant ( table 4 ) .
the mean value of cobalt concentration in glazers with dermatitis was 5.7g / l versus a mean of 2.54g / l among glazers without skin allergy ( table 3 ) .
ancova showed that , after adjusting for pre - shift cobalt , the effect of skin allergy on post - shift lead was significant ( table 4 ) .
results obtained after anocova for post - shift urinary cobalt by independent factors controlled for pre - shift cobalt tile glazers had a slightly higher urine cobalt level compare to the pottery glazers ( 3.39g / l versus 3.7g / l ) .
ancova showed that , after adjusting for pre - shift cobalt , the effect of job on post - shift cobalt was not significant ( table 4 ) .
glazers without protective masks or local exhaust ventilation during mixing or handling of glazes had significantly higher levels of cobalt compare to the glazers with protection ( 4.58 g / l versus 2.77
ancova showed that , after adjusting for pre - shift cobalt , the effect of masks and ventilation on post - shift cobalt was not significant ( table 4 ) .
glazers who had work history more than 21 hour showed higher urine cobalt levels compared to the glazers with overtime work less of 21(7g / l versus 2.75g / l ) .
ancova showed that , after adjusting for pre - shift cobalt , the effect of overtime work on post - shift cobalt was not significant ( table 4 ) .
in this study , the mean value of the urinary concentrations of cobalt in the glazers ( 3.47g / l ) was below the acgih biological exposure indices of 15 g / l ( 26 ) . however , cobalt is an important constituent of blue glazes , however , in time of sampling , because of ceramic characteristics , the use of this metal in glazes was somehow lower the normal . nevertheless , the glazers had a mean urinary cobalt concentration three to four times higher compared to the controls .
the subjects exposed to a soluble cobalt pigment in pottery painting had an increase in the urinary cobalt concentration ( 27 ) .
in contrary to the results obtained through this study , roig - navarro et al .
( 1997 ) have reported high urinary cobalt level in the ceramic factories ( 28 ) .
relationship of cobalt in the development of lung cancer has been studied among women exposed to the cobalt blue dye .
results showed the incidence of lung cancer slightly higher than the expected value ( 29 ) .
moulin et al . showed simultaneous exposure to cobalt and tungsten carbide causing lung cancer ( 30 ) . at the end of the shift , urinary concentrations of cobalt were higher than start of the shift levels , thus , results indicated that , cobalt is alimented immediately via urine .
this study also confirms that , urinary cobalt seems to reflect the amount of cobalt recently absorbed . since condition of workplaces such as ventilation system and glaze constituents did not change in the shifts , there was no significant difference between groups regarding to shift work .
this study also confirms the role of cobalt in occupational dermatitis similar to previous studies ( 31,32 ) .
exposure to cobalt can be reduced by improving skin protection and personal hygiene in workplaces ( 33 ) .
improperly ventilation and working without mask was associated with significantly higher levels of cobalt in the urine of glazers .
( 1985 have indicated the level of cobalt in the blood and urine 2.5 and 1.8 times ( respectively ) lower in the workers who used respiratory protection devices compared to those who did not use respirators ( 34 ) .
because of ceramic characteristics both pottery and tile glazers use glazes that generally contain the same amount of cobalt , therefore , this variable in pottery and tile glazers were not significant . in glazers with greater overtime work , due to more time exposure to cobalt , a significant increase in urinary cobalt level was observed . in the present study age , bmi , and work history were not significant variable .
however , the highest values of cobalt were recorded among older workers due to the unhygienic behavior , higher bmi and work history . in the present study ,
the decline in fev1 and the ratio of fev1/fvc was higher in those who have exposed to cobalt compared to those who have not exposed .
results obtained in this study showed a reduction in lung function , mainly of the obstructive syndrome type in the glazers .
these findings are due to the effect of both the glaze constituents and raw material used such as silica .
have reported exposure to silica related to reduction in pulmonary function and chronic obstructive pulmonary disease ( copd ) ( 35 , 36 ) . in another study , in ceramic workers in iran , respiratory complaints and abnormal pulmonary function
several studies have been indicated prevalence of chronic bronchial obstruction in relation to the cobalt exposure ( 38 , 39 ) .
raffn et al . among plate painters exposed to the cobalt blue dye showed increased respiratory symptoms and airway resistance ( 40 ) .
cobalt exposure is associated to a decline in fev1 in smokers who are exposed to cobalt ( 41 ) .
further studies are required to understand the mechanism of interaction between heavy metals and silica in prevalence impaired lung functions .
although cobalt poisoning occurred mainly among subjects who use cobalt for product blue colors in the ceramics , it could also occur in the general population during the normal use .
cobalt can be extracted into the food substances due to the improper formulation and firing of glazes .
acidic food and juice readily induce leaching of cobalt from glaze ( 42 , 43 ) .
cobalt is released by some of the dishes ( 44 ) . for reduction of cobalt exposure ,
workers should use respirators , not to eat or smoke at job position , separate work uniform from the other clothes to prevent the hazards of working with cobalt - containing glazes .
also , hygienic behaviors , washing facilities , and using proper personal protection equipments can be considered as effective means to reduce the cobalt exposures .
ethical issues ( including plagiarism , informed consent , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc ) have been completely observed by the authors .
 background : cobalt is one of the most important constituent present in ceramic industries . 
 glazers are the relevant workers when they are producing blue colored ceramic , causing occupational exposure to such metal . through this study , urinary cobalt was determined in glazers in a ceramic industry when they were producing blue - colored ceramic glazes.methods:in this case - control study , spot urine samples were collected from 49 glazers at the start and end of work shifts ( totally 98 samples ) in 2011 . 
 control group were well matched for age , height , and weight . 
 a solid phase extraction system was used for separation and preconcentration of samples followed by analysis by inductively coupled plasma - atomic emission spectroscopy ( icp - aes).all participants filled out a self administered questionnaire comprises questions about duration of exposure , work shift , use of mask , skin dermatitis , kind of job , ventilation system , overtime work , age , weight , and height . 
 the lung function tests were performed on each control and cobalt exposed subjects . 
 analysis of covariance ( ancova ) was used to evaluate the obtained results.results:urinary levels of cobalt were significantly higher in the glazers compared to the control group . 
 there were significant differences at urinary concentration of cobalt at the start and end of the work shift in glazers . 
 spirometric parameters were significantly lower in the glazers compared to the control group . among the variables used in questionnaire the significant variables were dermatitis skin , mask , ventilation , and overtime work.conclusion:this study verified existence of cobalt in the urine glazers , showing lower amount than the acgih standard . 
Introduction
Materials and Methods
Experimental
Sample preparation
Analysis procedure
Results
Discussion
Conclusion
Ethical considerations