When it comes to the debate on lead being used for shot or bullets, the debate is not if it's banned, more when it will be banned. The advocates for the banning of this material being used are vociferous in their assertion that lead in this form is harmful to all, and nothing but an outright ban will do to protect the flora and fauna of the countryside, and protect people from the effects of lead poisoning.
And on the face of it this seems to be a sensible stance to take, after all there is a long documented history of lead poisoning by man, on man. The Romans were most probably the first to use lead in large quantities; its abundance of natural deposits all over their empire, its relatively simply production method, and its ability to be cast at low temperature or worked with simple tools without the need for heat, and its imperviousness to water, all made lead a perfect metal for the time.
It was unfortunate for the Romans that the lead they used was still very soft and susceptible to oxidisation, as it is in its natural state when the ore bearing rock is exposed the atmosphere, the ore at the surface produces a white powder. In the Roman water pipes, relying mostly on gravity to make the water flow, there was insufficient pressure to force the water to all parts of the pipe. This resulted in pipes being filled to different levels when in use. When the levels were low the pipe would oxidise, then when the level rose, the oxide would be washed away in suspension within the water. This water, with the lead, would be consumed people, where the microscopic particles would eventually enter the blood stream. The Romans did not know this, but they did notice that water would taste sweet, and so they used the lead oxide to sweeten food. Through the century's, lead oxide was used in many, many products, until it was eventually found to be detrimental to health and in large enough quantities, poisonous.
As time passed man found ways to harness the positive attributes of lead by adding other materials to it to make it more stable. One of the first metals used to harden lead was arsenic, whilst this had the desired effect, the addition of arsenic made the lead more poisonous than ever, and any game shot would need to have the contaminated meat around the wound excised, thus making the rest of the animal edible. Later another metal, antimony, was used to harden the lead, in ratios from 0.5% to 25%. When used for shooting the lead antimony mix is between 2-8%, at this ratio the lead becomes much harder and therefore more stable, in addition, this small amount of antimony greatly reduces the rate of oxidisation to the point that lead shot these days rarely oxidises.
At this point I hear the question, "Then why is it banned in most countries around the world for shooting duck and other waterfowl, and over wetlands"? This is a simple answer really, due to the way that most waterfowl obtain and digest their food, lead can enter their bodies and blood stream. Most waterfowl feed by taking food in and then grinding the food up in the gizzard. This grinding process in the digestion of the waterfowls food is what allows shot to be ground into very small particles and thus enter into the blood stream or other areas of the bird's body. Other birds also have gizzards, what about them? Most waterfowl have bills, not beaks, this creates an inability to be able to be specific when finding food. A bird with a bill will puddle and filter food, but in the process take in small stones along with the invertebrates etc. that it feeds on. These small stones assist in the breakdown of food, but also breakdown any shot that may have been taken in. birds with beaks on the other hand peck their food and are able, to a degree, to discern between food and stones, thereby avoiding hard objects like shot entering their body.
The lead shot used in modern cartridges more stable than that used in the past, and when shot from a gun and dispersed into the environment presents no more risk of pollution than that of naturally occurring lead, and due to the antimony will sink below the surface long before it could oxidise.; once there the oxygen weak environment of the soil means that oxidisation process will be held back indefinitely.
So why all the furore over lead now, it's been used for centuries, its better managed now than ever, and science has ensured that when it is used, especially in shooting, it is safe. The answer to this is not straight forward, but in a nutshell, those that wish to stop hunting, shooting, and civilian gun ownership around the world, came up with a lead ban. The reason for banning lead is that without it, ammunition to a degree would not exist, as replacement and alternatives are either non-existent or very expensive. In order to assist their argument these groups have and are using their usual weapons, misinformation, fear, and emotion.
The misinformation source is the based around the use of lead in the chemical and petro-chemical industries, as in lead in petrol/gas. The science was undertaken and evaluated and the lead particulates in the atmosphere were proven to harmful to all. They are now taking this evidence, as evidence of lead in shooting, being of equal harm to the environment and humans. This is patently not true, and there is no evidence to support this assertion.
The fear mongering, in the face of evidence to the contrary, has centred on game taken by shooting. Lead shot or fragments (metallic lead), if taken and ingested in the normal course of eating a meal, will pass through the digestive tract without any side effects. This is quite different to the effects of someone ingesting soluble forms of compounded lead found in industrial products, such as leaded paint, gasoline and pesticides, the lead is readily absorbed in the body and increases blood-lead levels significantly.
Finally emotion, animal rights groups are especially adept at the manipulation of emotion in order to achieve their goals, and they have lent their vast skill and knowledge to the cause of banning lead in ammunition. A good example of this is plight of the California condor. In the tracts of land where this bird presides, legislation was passed that no lead ammunition could be used by anyone for any purpose. Since the bill to prohibit the use of lead in these areas, to protect the condor, and with a compliance rate from the hunting community of over 98.89%; the 2009, 2010, and 2011 condor blood-lead data, collected by the Condor Recovery Program in California, shows that the incidence of lead exposure and poisoning in condors remains static and has actually increased slightly.
Governments around the world, along with unelected bodies such as the United Nations, are promoting this and other erroneous causes in an effort to remove firearms from civilian ownership. Whilst in many cases the direct approach has failed, the removal of either a component or material used in the manfacture of firearms and related ephemera can, will, and does have a huge effect. So when lead is banned outright, do not be surprised to see that copper bullets are dangerous to the environment as they degrade naturally in the soil.