The two scientists suggested that federal safety guidelines for low-level exposures be reduced by 90 percent in 1969.

The studies may also give scientists valuable insights into the biological effects of low-level exposures to radiation.

The effect on humans of low-level exposure over an extended period has not been extensively formally studied.

There are few studies exploring the effects of long-term low-level exposure to sulfur gases.

She added, "We would have been very much more interested in additional research on low-level exposure, which still needs to be done."

But the report cautioned then that "virtually nothing is known" about long-term health effects of low-level exposure to the chemicals.

But lead from peeling or chipping paint can result in low-level exposure, especially to children.

A 2002 study suggested that persistent low-level exposure to lead may also increase the risk for gout.

It is unknown whether low-level chronic exposure may cause permanent neurological damage.

We really don't have good data on what health effects are caused by long-term, low-level exposure to those agents.