Arsenic is a ubiquitous environmental toxicant, found in high concentrations in water worldwide; more than 150 million people live in areas with the arsenic content significantly higher than the WHO and USEPA recommended guidelines (10 ppb).The lung is a target organ for arsenic toxicity. Reports from human studies in Chile, Bangladesh, Inner Mongolia and the West Bengal region of India show that chronic exposure to arsenic via drinking water is correlated with increased incidence of chronic cough, chronic bronchitis, shortness of breath, decreased lung function, and obstructive or restrictive lung disease. Evidence from our laboratory and others have contributed to a growing concern that even at 10 ppb, arsenic can alter lung structure and function. In addition, there is also growing evidence that in utero and early postnatal exposures to arsenic can lead to alterations in lung structure and function that contribute to the development of chronic lung disease later in life. In rural areas of United States such as in the southwestern region, a significant percentage of the population receives their water from private, unregulated wells where concentrations of arsenic can far exceed the 10 ppb level. In addition, dusts in the arid Southwestern United States can contain high levels of arsenic and other contaminants. Inhalation of these dusts can increase lung exposures to arsenic that mimic arsenic ingestion induced lung disease. Little data exist concerning the risk from exposure to arsenic containing dusts and the potential interactions between arsenic ingestion in water and dust exposures. Despite the accepted fact that the lung is a major target organ for arsenic toxicity, studies on biomarkers or mechanisms of non-malignant lung diseases following early life arsenic exposures are limited.