A train in New Jersey has derailed causing hazardous chemicals to spill, including vinyl chloride.
Short-term exposure to high amounts of that chemical can lead to dizziness, drowsiness and headaches, according to the Environmental Protection Agency.
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It will be increasingly humid and thundery with highs of 30C or more today.
Holidaymakers in Tunisia are determined not to be beaten. But, as Neil Connery writes, it won't be easy to escape the shock of the massacre.
Drink lots of water, stay out of the sun during the middle of the day, and take particular care of vulnerable people.