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It was also found that e-cigarettes contain a number of dangerous chemicals including acetaldehyde, acrolein and formaldehyde.

Blood and urine will be screened for exposure to chemicals present or suspected to be present at the derailment, including dioxins, vinyl chloride, acrolein and butyl acrylate.

But the researchers did detect levels of acrolein — a chemical irritant that affects the eyes, skin and respiratory system — that were three times as high as those in downtown Pittsburgh, some 80 kilometres away.

But acrolein levels were high enough in some places to raise long-term health concerns, said Albert Presto, a Carnegie Mellon mechanical engineering research professor.

Wood-burning devices emit pollutants known to make people sick, including fine particle pollution and chemicals like benzene, formaldehyde, acrolein and polycyclic aromatic hydrocarbons.