For waterfowl hunting in the United States, only non-toxic shotgun pellets are allowed. Lead shot is prohibited nationwide since 1991 due to its toxicity to waterfowl and environmental contamination

. Approved types of non-toxic shot include:

• Steel shot (iron and carbon)
• Bismuth-tin shot (97% bismuth, 3% tin)
• Various tungsten-based shot types, such as:
  • Iron-tungsten
  • Iron-tungsten-nickel
  • Tungsten-bronze
  • Tungsten-iron-copper-nickel
  • Tungsten-matrix
  • Tungsten-polymer
  • Tungsten-tin-iron
  • Tungsten-tin-bismuth
  • Tungsten-tin-iron-nickel
  • Tungsten-iron-polymer
• Copper-clad iron
• Corrosion-inhibited copper

These shot types must meet density and hardness standards to be effective and safe for waterfowl hunting

. Additional regulations:

• Shot size must be size T (0.20 inches in diameter) or smaller

• Use of lead shot or lead-plated shot is illegal for waterfowl hunting

• Violations can result in fines and suspension of hunting privileges

In summary, hunters must use approved non-toxic shot types such as steel, bismuth, or tungsten-based pellets when hunting waterfowl in the U.S. This protects waterfowl from lead poisoning and complies with federal regulations enforced by the U.S. Fish and Wildlife Service