The U.S. Supreme Court has refused to throw out a number of class-action lawsuits that challenge radiation emissions from cell phones.

With Chief Justice John Roberts presiding, the court refused to consider an appeal from cell phone manufacturers, who wanted the high court to overturn a decision by the 4th U.S. Court of Appeals in Richmond.

Class-action lawsuits currently pending in Maryland, New York and Pennsylvania allege that cell phone radiation can cause brain tumors. The suits allege the manufacturers are aware of the danger and have deliberately kept consumers in the dark.

The suits seek to force phone manufacturers to reduce the amount of radiation produced by phones, and to advise users of the alleged health hazards.

In 2004, Judge Catherine Blake dismissed five of the lawsuits. But in March the appeals court ruled 2-1 that four of the five cases must be sent back to lower courts for trial.

Motorola, Nokia, Nextel Communications, Sprint and Cingular Wireless are among defendants named in the lawsuits.