Silicosis is well-known occupational disease caused by free crystalline silica (silicon dioxide) and is marked by inflammation and pulmonary fibrosis. There are cumulative evidences that exposure to Caesar stone (quartz surface products that manufactured from up to 93% quartz, polymer resins and pigments) is particularly dangerous to exposed workers.

Goals: To examine correlation between disease and exposure to Caesar stone and genetic differences regarding genes involved in oxidative stress to understand Genetic susceptibility

It is a sub-study of "DNA-damage biomarkers to monitor and early detect health impairment in workers exposed to Silica (Caesar Stone)" study. Study participants would be recruited during two years of the study. They will be asked to come to a single visit at Pulmonary Laboratory of Tel Aviv Medical Center. During the meeting, participants will be given a precise explanation about the tests they will perform and after signing the informed consent will perform following tests:

1. Induced sputum (IS)
2. Exhaled Breath Condensate
3. Pulmonary function tests (PFTs)
4. Participants will be asked to complete occupational questionnaire

Genetic studies (DNA) will be done from peripheral blood samples (20 ml) to study differences in Heme oxygenase 1 (HO-1) gene sequencing between participants with evidences of clinically definite silicosis according to American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines and participants without evidences of clinically definite silicosis.DNA samples will be obtained and coded in the same day of a participant visit and after collecting reasonable amount of samples examination of genes of interest will be done.Analysis of data will be done after the completion of data collection and laboratory tests.

Each sample will be given specific code to protect confidentiality of participants. Blood samples, test results and the code key will be kept in different places and only few research staff will have the accessibility to genetic information. In any case employers or any other persons that not included in research staff will not have any accessibility to this information. In this study genetic analysis is not connected to gender, nationality or any other social feature.

Inclusion Criteria:

1. male
2. 18-70 years old
3. At least six months of professional exposure to Caesar stone

Exclusion Criteria:

1. Other occupational exposure (welding of any kind)
2. Chronic Obstructive Pulmonary Disease (COPD), tuberculosis, asthma, autoimmune disease in healthy exposed workers
3. Interstitial lung disease in exposed workers with clinically approved silicosis

At least six months of occupational exposure to Caesar stone