Tens of millions of Americans suffer from nasal allergies caused by exposure to trees, grass, and weed pollens. Additionally, approximately 37% of Americans live in a county with ragweed pollen — a seasonal allergen — and unhealthy levels of ozone, which can induce allergic reactions such as itchy eyes, nasal congestion, and watery eyes in people with nasal allergies. Living in such areas can contribute to negative health effects in young children, older adults, people who work or exercise outside, people with asthma, and other sensitive groups.
Ground-level ozone is the main ingredient in smog. The degree of exposure to harmful smog and ragweed pollen varies throughout the country and can be made worse by pollution. Areas with ragweed pollen and a high number of unhealthy ozone days are worse for people with nasal allergies and asthma, and tend to be the parts of the country most vulnerable to climate change.
To determine the worst county for allergies in every state, 24/7 Wall St. ranked counties according to the average number of unhealthy ozone days and the presence of ragweed pollen with data from the Environmental Protection Agency and the Center for Invasive Species and Ecosystem Health at the University of Georgia.