Which of the following is true about pneumoconiosis?

Lung cancer is the most common cancer associated with asbestos exposure.There is a significant inter-active effect of smoking and asbestos exposure that results in greater risk than what would be expected from the additive effect of each factor. Asbestos related pleural plaques,paicularly along the lower lung fields,the diaphragm, and the cardiac border,imply only exposure ,not pulmonary impairment & without additional manifestations.Since silica is cytotoxic to alveolar macrophages,patients with silicosis are at greater risk of acquiring tuberculosis. Reference:Harrison's medicine-18th edition,page no:2123-2125.