22. If it is not possible to determine which defendant in an action brought on an individual basis caused or contributed to the exposure to a type of tobacco product of particular health care recipients who suffered from a disease or a general deterioration of health resulting from the exposure, but because of a failure in a duty imposed on them, one or more of the defendants also caused or contributed to the risk for people of contracting a disease or experiencing a general deterioration of health by exposing them to the type of tobacco product involved, the court may find each of those defendants liable for health care costs incurred, in proportion to its share of liability for the risk.