Please check the following links and the pdf attachments for the answer.

http://link.springer.com/article/10.1385%2FBTER%3A111%3A1%3A63#page-1

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517040/

http://www.wha-www.org/en/library/library.php?studies=tuberculosis

http://www.sciencedirect.com/science/article/pii/S0366085037800976

Air particulate contaminants including heavy metals interfere with the respiratory system as they deposit on the trachea alveolar system, depending on their aerodynamic diameter, since tuberculosis is a pulmonary disease, any alteration in the biochemical, anatomical and physiological integrity of the respiratory organs will exacerbate tuberculosis. Heavy metals are implicated in the etiology of cellular oxidative stress,  distorting  cell membrane structure thereby increasing the invasive ability of the tuberculous pathogens.         

Dear Dr Pach

I agree with what you say. I don't want to toxicate any mice or people. I want to study concentration of heavy metals in people who have already tuberculosis and are encountered with air pollution in every day life. You know, I want to say in this investigation that our patients have not good condition. I asked you about confounding factors to eliminate any other factor except the studied factor.