But these bouts of harshness are usually briefand the researchers wanted to know how the sharks might cope with more chronic exposure.

The two groups share chronic exposure to fright hormones.

But science suggests that chronic exposure to multiple bioactive substances may well harm human health, even at low levels.

Chronic exposure to humans may cause kidney damage.

Several studies using cultured cells and laboratory rodents suggest the possibility of leukemogenic, and of genetic, reproductive, and neurological effects from chronic exposure.