Wildfire smoke contains hundreds of chemical compounds, and many can be harmful in large amounts. Smoke from burning houses and buildings contains even more toxic chemicals. This is from all the manufactured materials. Growing scientific research points to possible long-term health damage from breathing in very small particles of smoke. These long-term health problems include decreased lung function, weakened immune systems and higher rates of flu. There are short-term issues as well. At-risk people can be hospitalized and sometimes die from breathing in large amounts of smoke, say doctors and public health officials. Officials in the U.S. have been moving quickly to better protect people from the harmful effects of wildfire smoke. However, they find it more difficult to communicate these dangers to communities and people who live thousands of kilometers from the fires. Jeff Pierce is an atmospheric scientist at Colorado State University. He said smoke loses its odor. But it remains harmful even when it travels very far. “It is certainly unhealthy,” Pierce said of the air along the eastern U.S. coast in recent days. “If you have asthma or any sort of respiratory condition," he said, you may want to change your plans if you’re going outside. A recent study by Pierce and Sheryl Magzamen, another Colorado State University scientist, found that people who live close to fires are more likely to be prepared. However, those who live farther away may not know of the dangers.