Fog sweeps the US with reports of chemical smell' & illness

As thick fog had swept across the US in multiple states, citizens have been reporting how a 'burning chemical-like smell' has blanketed their communities. Some witnesses have also claimed the fog has also triggered health symptoms.
Link:
https://www.dailymail.co.uk/sciencetech/article-14239417/thick-fog-mystery-chemical-smell-reports.html