toluene diisocyanate ( tdi ) is an imperative chemical substance used in the production of polyurethane foams , elastomers , paints and coatings and cause a variety of health problems in workers who are exposed in work places ( 1 ) .
health effects that induced by tdi consist of asthma , chronic obstructive lung disease , hypersensitivity pneumonitis , alveolitis , conjunctivitis , and rhinitis ( 2 ) .
the ability of tdi and the other diisocyanates to cause respiratory hypersensitivity is well known ( 3 ) . occupational asthma ( oa ) is a respiratory disorder express by bronchial hyper reactivity caused by agents present in the air in the workplace ; it causes obstruction or sensitivity of the airways and is partly or completely reversible , instinctively or by treatment ( 4 ) . with increasing rate of asthma morbidity and mortality rate in many developed countries over the past 1020 years ( 5,6 ) , the incidence of oa is rising , because of increased exposure to work related toxic agents .
although it is a quite frequent disorder , the roles of smoking and atopy in its pathogenesis are not totally known ( 7,8 ) .
although many clinical and epidemiological studies have been carried out to evaluate the effects of exposure to tdi in workplaces on human health , many questions remain unanswered .
it is the first time in iran that tdi effects on exposed workers are assessed .
this study aimed to determine the asthma symptoms and serum specific ige levels in tdi exposed workers and comparing the results with healthy control group .
all the plants that use tdi in the manufacturing of paint and glue in the west of tehran province entered to the study and all the workers ( 550 ) completed modified initial questionnaire of the niosh .
the questions were consist of asthma symptoms such as wheezing , cough , chest tightness , shortening of breath , cigarette consumption , number of daily cigarette consumption , family history of allergy and work duration .
total ige and specific tdi ige tests were done for 26 workers who had asthma symptoms by rast method with r - biopharm , darmsiasi , germany . for each symptomatic
exposed worker one worker selected as control if met these inclusion criteria : 1- sex and age matched 2- non asthmatic 3- did not exposed to tdi in work places .
questions about cigarette consumption , number of daily cigarette consumption , and family history of allergy were asked from selected control group .
total ige and specific tdi ige test were carried out for control group such as symptomatic exposed workers .
data were analyzed by spss version 18 to calculate chi square test and or ( odds ratio ) and 95% cis ( confidence interval ) .
paired samples test was used to compare total ige means in exposed and unexposed groups .
all the plants that use tdi in the manufacturing of paint and glue in the west of tehran province entered to the study and all the workers ( 550 ) completed modified initial questionnaire of the niosh .
the questions were consist of asthma symptoms such as wheezing , cough , chest tightness , shortening of breath , cigarette consumption , number of daily cigarette consumption , family history of allergy and work duration .
total ige and specific tdi ige tests were done for 26 workers who had asthma symptoms by rast method with r - biopharm , darmsiasi , germany .
for each symptomatic exposed worker one worker selected as control if met these inclusion criteria : 1- sex and age matched 2- non asthmatic 3- did not exposed to tdi in work places .
questions about cigarette consumption , number of daily cigarette consumption , and family history of allergy were asked from selected control group .
total ige and specific tdi ige test were carried out for control group such as symptomatic exposed workers .
data were analyzed by spss version 18 to calculate chi square test and or ( odds ratio ) and 95% cis ( confidence interval ) .
paired samples test was used to compare total ige means in exposed and unexposed groups .
all of the workers were male and the mean age of symptomatic workers was 36.38 8.49 yr . among 550 tdi exposed workers 26 ( 4.7% ) workers had asthma symptoms . among symptomatic workers ten workers ( 38% ) stated that they ever had asthma but 9(34.6% ) had physician asthma diagnosis .
details of asthma symptoms including the frequency of wheezing , breath shortness , cough , and chest tightness are presented in table 1 .
other allergic signs were observed concomitantly with asthma symptoms : 17(65.4% ) allergic rhinitis , 14(53.8% ) eye allergic and 15(57.7% ) skin allergic cases were observed .
nine ( 34.6% ) of workers who were exposed to tdi were active cigarette consumer versus 3(11.5% ) unexposed workers , or=4.059 ( ci= 0.95317.29 ) p=0.049 ( table 1 ) .
six ( 23.1% ) of exposed workers consumed daily more than 5 cigarettes in comparison with 2(7.7% ) unexposed workers or=0.278 ( ci=0.0501.531 ) p=0.124 .
nine ( 34.6% ) of paint and glue plants workers had positive family history of atopy versus 1(3.8% ) unexposed workers , or=13.24 ( ci= 1.45305.41 ) p=0.0138 ( table 2 ) .
tdi specific ige was found in 2 tdi exposed workers and 1 unexposed worker ( p=0.5 ) .
mean of total ige was 339.05 iu / ml in exposed workers in compare of 52.19 iu / ml in unexposed workers ( p=0.201 ) .
all the workers with positive specific ige ( 2 workers ) were exposed to tdi more than 10 years .
range of work duration in plants that consumed tdi was 127 years with mean of 10.586 .
isocyanates cause a variety of respiratory disorders such as occupational asthma ( oa ) with prevalence of 5% to 10% in exposed workers ( 9 ) .
other uncommon diseases like allergic alveolitis , and systemic symptoms also occur ( 10 ) . in our study
, we found 26 ( 4.7% ) of tdi exposed workers had asthma symptoms that appears less than the other reported rates ( 1114 ) .
this difference may be related to the plants structure in west of tehran province , in the environmental observation of factories we found that the major parts of production have been carry out in the open places of plants such as yards .
the work in the open places leads to decrease the tdi exposure and consequent low symptoms among workers .
oa that was induced by ige - dependent agents is similar to clinical and pathologic features of allergic asthma that is not related to work ( 15,16 ) .
specific ige antibodies to tdi have been reported in a range of 0% to 40% ( 17,18 ) . in this study we found specific ige in 2 symptomatic exposed workers and one unexposed worker that did not show statistically significant relation between specific ige and clinical symptoms of asthma , also we did not have any significant association of total ige in two groups .
we should consider that although the presence of ige antibodies is highly diagnostic but it has no sensitivity in detecting isocyanates induced oa .
it can be explained by the presence of more than one immunologic mechanism of respiratory sensitization in isosyanate induced asthma including ige antibody - independent mechanisms ( 19,20 ) . in comparison of our clinical findings
littorin et al . in 2007 reported bronchitis 10% , cough 28% , cough with mucus 34% and wheezing 27% in tdi exposed workers ( 21 ) .
our study showed that use of cigarette increases the risk of asthma symptoms 4 folds in tdi exposed workers , or=4.059 ( ci= 0.95317.29 ) p=0.049 , however we could not find any association between daily cigarette consumption and asthma symptoms . in agreement of our findings
. showed that cigarette consumption is significantly higher in oa patients due to tdi ( p=0.012 ) ( 14 ) whereas siracusa et al . found no relation between tdi induced oa and smoking ( 22 ) , these contradictory results can explained by the  healthy smokers effect  healthy workers have more chance to get a job and continue it because they suffer less and their employer like to keep them rather than their unwell colleagues ( 23 ) .
we showed family history of atopy elevates the risk of asthma symptoms in tdi exposed workers versus unexposed workers or=13.24 ( ci= 1.45305.41 ) p=0.0138 .
stated genetic factors can influence disease susceptibility because tdi induced asthma symptoms only in a small part of exposed workers can be detectable ( 24 ) and many researches were carried out to detect the influencing gens ( 2529 ) .
this study provides clinical and paraclinical data of workers who are exposed to tdi and points to a relation between atopy and smoking habit with asthma symptoms that offer preventing recommendations for tdi exposed workers and their heath administrators however further studies in this field is recommended .
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 .
 backgroundtoluene diisocyanate ( tdi ) is an imperative chemical substance used in the production of polyurethane foams , elastomers , paints and coatings that cause a variety of health problems in workers who are exposed in work places . 
 this study aimed to determine the asthma symptoms and serum specific ige levels in tdi exposed workers and comparing the results with healthy control group.methods:all the plants that use tdi in the manufacturing of paint and glue in the west of tehran province entered to the study and all the workers ( 550 ) completed modified initial questionnaire of the niosh , the questions were consisted of asthma symptoms . for each symptomatic exposed worker one healthy , sex and age matched control selected . 
 total ige and specific tdi ige tests were done for each case and control groups.results:among 550 tdi exposed workers , 26(4.7% ) had asthma symptoms . nine ( 34.6% ) of symptomatic workers who were exposed to tdi were active cigarette consumer versus 3(11.5% ) unexposed workers , p=0.049(ci= 0.95317.29 ) or=4.059 . 
 nine ( 34.6% ) workers had positive family history of atopy versus 1(3.8% ) unexposed workers , p=0.0138 ( ci= 1.45305.41 ) or=13.24 . 
 tdi specific ige was found in 2 tdi exposed workers and 1 unexposed worker ( p=0.5 ) . 
 mean of total ige was 339.05 in exposed workers ( p=0.201).conclusion : this study provides clinical and paraclinical data of workers exposed to tdi and points to a relation between atopy and smoking habit with asthma symptoms that offer preventing recommendations for tdi exposed workers and their heath administrators . 
Introduction
Materials and Methods
TDI exposed workers
TDI unexposed workers
Analysis
Results
Discussion
Conclusion
Ethical considerations