[MUSIC] Hello everyone. In this video, let's focus on talking about the health effects of bioaerosols. Bioaerosols can cause allergies. Acute symptoms from bioaerosols include malaise, fever, shortness of breath, dizziness, coughing, and muscle pains. Those symptoms are part of the sick building syndrome. Bacteria and viruses may cause respiratory infections. Bioaerosol particles with ten microns in diameter deposit in the nose and throat, while particles of five to ten microns in diameter go deeper into the upper and lower respiratory tract. While particles of two to five microns enter the lungs and conducting airways. Particles less than two microns in diameter even go deeper into the gas exchange area, the alveolar region. Besides respiratory infections, bioaerosols are one type of allergen. People with allergic asthma are very sensitive to allergens. Once allergens are inhaled, symptoms of asthma are developed, such as excessive secretions in the bronchi, spasm of smooth muscle in the bronchi wall, and inflammatory swelling of the bronchial lining. Legionella is a type of bacteria that can lead to Legionellosis, which is a kind of respiratory infections. The severity of Legionellosis varies from less serious respiratory illness called Pontiac fever to a potentially fatal type of pneumonia called Legionnaires' disease. Pontiac fever is an acute, self-limiting, influenza-like disease without pneumonia. Pontiac fever has a high attack rate. Up to 95% of those exposed to Legionella suffer from Pontiac fever indiscriminately. The incubation period is the time between initial exposure to the infection and the appearance of the first symptom of, or sign of disease. The incubation period of Pontiac fever is a few hours and up to three days. It lasts for about two to five days normally. Treatment is normally performed to relieve symptoms. Legionnaires' Disease, LD, is a type of pneumonia that has no typical symptoms or signs. LD often initially causes anorexia, discomfort, and lethargy. Patients may develop a mild and unproductive cough. Fever is also one of the common symptoms. The attack rate of LD is low. Only about 2 to 5% of those exposed to Legionella suffer LD. The average incubation period of LD is two to ten days, although it may extend to more than ten days in some cases. If no treatments are taken, patients usually get worse during the first few weeks and may lead to death. Patients may suffer complications such as respiratory failure. Patients could have appropriate treatments in the early stage can usually recover. There are some kinds of people who are more at risk to LD. Men are twice as likely as women to get LD. Besides, people over 50 years old, heavy smokers, and alcoholics, and people with chronic disease or an impaired immune system are more susceptible to LD. Legionella survive and reproduce in water at temperatures between 25 and 45 degrees Celsius with an optimal temperature range of 32 to 42 degrees Celsius. Legionella can stay in an environment with temperature up to 70 degrees celsius but are destroyed at temperatures above 70 degrees Celsius. Legionella are acid-tolerant, and they survive in an environment with pH values between 2.7 to 8.3. As Legionella can easily develop in water under room temperature, Legionella can be found in stagnant water systems of a building, such as cooling towers, water tanks, and water distribution system. Besides, stagnant water systems containing microorganisms, like algae and amino acids, like L-cysteine-HCL, and iron salts, can also facilitate Legionella to grow. In summary, there are three factors contributing to the infection of LD. First, a person is exposed to airborne droplets or particles in fine mist containing Legionella bacteria. Then the person inhales those particles, and the person is susceptible to LD. As mentioned, Legionella can be found in the water system of a building. To prevent the spread of Legionella, the water system should be well-designed and cleaned regularly. Take a cooling tower as an example. First, the cooling towers should be site as sufficiently far away from any public passage and air intakes of ventilation systems. As a result, it makes difficulty for the Legionella and the cooling towers to enter the building. Besides, the surface material of the cooling towers should be smooth and easy to clean. In addition, the inner surface of the cooling towers has to be cleaned regularly to remove microorganisms generated. And effective drift eliminator should also be installed to prevent the escape of water drops that may be contaminated to the surrounding environment. Moreover, chemical treatment should be performed regularly to clean the cooling towers. To conclude, in this video, we discussed the health concerns associated with bioaerosols. Then we focused on discussing Legionnaires' disease, LD. Its health effects, sources, and some cooling towers design recommendations for the prevention of LD.
