Ground-Level ozone is harmful to health, especially for children, the elderly, outdoor workers and those with respiratory conditions such as asthma. Particle pollution affects these people as well as those with heart disease. The primary target is the respiratory system, but it also targets the heart and the immune system. Ozone is a reactive and irritating chemical. When inhaled, it can irritate and inflame the airways that carry air from the mouth and nose to the lungs.