The causality is difficult problem which is still in development. Recently the Supreme Court of UK came to a very radical solution.
He granted a full compensation for a damage suffered from the company where she used to be employed. But to a substantial extend the personal injury has been caused by environment where she used to live.
Since the science is not able to evaluate the portion of the causation coming from the environment, the Court concluded, that the compensation should be paid in full amount by the company.