First rainfall since Tianjin explosion leaves city covered in mysterious white foam The first rainfall to wash over Tianjin since a series of blasts struck a warehouse in the Binhai district last week has sparked a new wave of concern as an unidentified white foam has appeared on the streets. Some who made contact with it are reporting a burning sensation on their face and lips, while others are reporting a stinging sensation on their arms. Some have said they experienced an itchy sensation, according to a NetEase News report.