IStock Photo 9040317 © Tulay Over

Hear that wheezing sound all around? More people have asthma than ever before—and kids from lower-income families who grow up in urban areas may have the highest rates of all. More than 16.2 million Americans (including 6.7 million children) have the chronic respiratory disease, according to a report last year from the Centers for Disease Control.

For adults, the odds of having asthma at any time in life are 1 in 9.15. However, in families living below the poverty level, the odds of having asthma are greater: 1 in 6.96. In children, the odds of having ever had asthma are 1 in 7.68, but in families living below the poverty level, the odds are 1 in 6.17.

Poverty, environment, and race are all factors in asthma prevalence, but it’s not easy to parse how much each matters. A 2008 report found that 19% of children from Puerto Rico and 13% of black children have asthma, compared with 8% of white children. Children from poor families are also less likely to see an asthma specialist when they do go to the doctor and to miss more school days because of the disease. Asthma is one of the most common chronic illnesses, but it requires nearly constant monitoring and treatment. Families without health insurance or access to regular medical care often find their ability to take preventative measures limited, and the emergency room becomes their doctor’s office.

The causal relationship between environmental factors and asthma is not clear and some data appear contradictory. In 2002, a study found that children who grew up in extremely clean homes were more likely to develop asthma and hay fever than those who grew up in homes filled with more dust and microbes. This is called the hygiene hypothesis. The theory is that the use of antibiotics combined with cleaner homes, indoor plumbing, and all our other modern amenities is keeping kids away from germs—and that’s making them less healthy. Without early-life infections, the immune system doesn’t properly develop, researchers say. Ironically for those who take care to sweep the dust bunnies gathering under the crib, that very fastidiousness can lead to asthma in children.

While the underlying causes of asthma continue to be investigated, a nation of wheezing kids can hold onto hope. Many people who have the condition as a kid go on to live symptom-free as adults.