I copied this out of the NH Fish and Wildlife site under fishing, Get the Lead out. It says you can drop off lead sinkers at their offices.
Keep Getting the Lead Out -- It's the Law!
Loons and other waterbirds can die from lead poisoning after swallowing lead fishing sinkers and jigs lost by anglers. In fact, according to the Loon Preservation Committee, poisoning from lead fishing tackle accounts for 52 percent of mortalities among adult and immature loons from 1976 through 2000. That’s by far the largest single cause of adult loon mortality in New Hampshire.
State law prohibits the use of lead sinkers and jigs in freshwater lakes and ponds in New Hampshire. The ban prohibits the use of lead sinkers weighing 1 ounce or less and lead jigs less than 1 inch long along its longest axis.
What you can do:
Use non-lead sinkers and jigs. It’s the law.
Ask your local sporting goods store to stock non-lead fishing tackle.
Spread the word. Tell other anglers about the problem with lead.
Dispose of old lead sinkers and jigs properly. Drop-off locations include all N.H. Fish and Game offices and hatcheries.
The law is intended to protect loons and other diving waterbirds that can accidentally ingest toxic lead sinkers as they pick pebbles up from lake bottoms. The pebbles grind food in the birds' gizzards to help their digestion.
Anglers can safely dispose of their old lead sinkers and jigs at:
All Fish and Game regional offices (Concord, Durham, Keene, Lancaster, and New Hampton) and state fish hatcheries (for locations, call 271-3211).
Household Hazardous Waste Collections held throughout the state held from April through June. Call the Department of Environmental Services at (603) 271-3503, or visit:
www.state.nh.us/des/hhw.
The Loon Preservation Committee's visitor center on Lee's Mills Road in Moultonborough.
For a free brochure ("Let's Get the Lead Out"), call Fish and Game's Aquatic Resources Education Program at (603) 271-3212.