There are many conditions that cause water or fluid in the lungs, according to Mayo Clinic, but most are related to the heart and a condition known as cardiogenic pulmonary edema. Other causes include high altitudes, drug reactions and exposure to toxins.
Coronary artery disease causes the arteries to narrow and lowers the effectiveness of the heart in pumping blood. This blood begins to collect in the lungs and the fluid from the blood leaks into the lungs, reports Mayo Clinic. This condition is known as congestive heart failure.
People who live, work or play at altitudes above 8,000 feet may develop a condition known as high altitude pulmonary edema. HAPE seems to develop due to the constriction of capillaries in the heart. While it is possible to minimize the risks, Mayo Clinic indicates the condition is sometimes fatal.
Certain drugs, including the street drugs heroin and cocaine and over-the-counter medications such as aspirin can cause fluid in the lungs. These adverse reactions are other causes of pulmonary edema, according to Mayo Clinic.
Toxins from the environment and even the body itself can cause fluid on the lungs. People who aspirate stomach acid from the esophagus to the trachea and lungs develop fluid accumulations. Chemicals including ammonia and chlorine cause irritation that leads to fluid buildup. Smoke also contains similar irritating chemicals, reports Mayo Clinic.