Tougher regulations to prevent zebra mussels in Great Lakes prohibited
A group of zebra mussels, taken from Lake Erie, are shown in this 2009 file photo. (U.S. Department of Agriculture)
A U.S. Senate committee has voted to create a national standard for ballast water discharges from commercial ships and prohibit states from imposing tougher requirements.
The bill cleared the Commerce, Science and Transportation Committee on Thursday and heads to the full Senate.
Ballast water keeps ships stable in rough seas, but it often harbours invasive species from other countries that escape when the water is discharged.
Zebra and quagga mussels have reached the Great Lakes in ballast water and environmental groups say Great Lakes states should be able to exceed federal requirements when necessary to protect their waters.