If I may provide some insight into this topic, of lead..
I have been heavily involved with birds of prey since the 70's. In the 80's was part of the group that reinstated the peregrine falcon in the Grand Rapids Michigan Area. ( your free to look that up)
Heavy research was conducted prior, and lead was the least of the problems. Main cause of decline was eggs so brittle they broke. And many females died because of broken eggs inside. Industrial chemicals from farmers.
I'm currently part of the Osprey nesting program in and around northern michigan. My favorite raptor.
A report and study done by MSU, the dept natural resourses, and dept of aguculture, showed much of the problem in decline of many species.
Acid rain, Calcium depletion , inorganic acids, such as nitric and sulfuric acid, falls out of the atmosphere as rain, snow, mist and fog. Fallen, decaying leaves and other natural litter on the forest floor could decompose more slowly under acidic conditions. Which in turn depletes calcium in plants and soil, critical at egg-laying time, when calcium demand is highest for female birds, or during the period, when calcium supplements are often provided to growing young.
Low levels of soil calcium might also affect a wide range of prey which other predators eat. Acidic conditions also increase the amounts of toxic aluminum and heavy metals (such as lead, cadmium and mercury) in small prey, this is injested by other predators that feed on them.
Kestrels for example, They had elevated stress hormones and high rates of nest abandonment from chemical contamination.
There is a strong relationship between human population density and the number of threatened mammal and bird species at a given point in time.
If we get to 11 billion people population in the world, which is where we're supposed to peak, then the amount of space you have per person is a lot smaller. When you're left with less space, there's virtually no space left for most all other species.
With the stopping of China buying our recycling in many many states, this will all ( as it currently is) ends up in land fill, and causes a big big problem for many species of animals. Tins, aluminum, plastics, you name it that China used to take from us...not any more.
Lead from bullets accounts for less than 1 %.
of the overall problem.