Nearly 120,000 babies will be born with birth defects this year. 

While there are a number of causes — genetics and chromosomal issues, infections during pregnancy, maternal malnutrition and exposure to certain medicines, illicit drugs and alcohol — one well-documented cause is exposure to environmental pollution. 

In freeway-lined Southern California, an estimated 2.5 million residents live in high-pollution zones (defined as less than 1,000 feet of a freeway), potentially putting pregnant women at greater risk of birth defect than their rural counterparts.

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