But it is a problem. For example, six years ago, three civilians were killed and fifty wounded in Baghdad, Iraq by gunfire associated with the Iraqi team winning a game during the Asian Games. Parents in Iraq know to get the kids inside when this kind of shooting starts. This was all about the widespread Arab custom of firing weapons into the air on happy occasions (they are called "joy bullets" in Arabic), often with deadly consequences. For a long time, when someone was killed or injured by the bullets that inevitably came back to earth the injury was shrugged off, or blamed on a handy enemy. Palestinians blame Israelis, some Iraqis blame any armed foreigners in the vicinity or nearby Iraqis they don't get along with. Otherwise it's just "God's Will." In many parts of the world it took decades for people to accept that these mystery bullets were the unfortunate aftereffects of celebratory firing into the air.
Such use of joy bullets is actually widespread. While such behavior is generally banned (and the ban enforced) in Europe, in the rest of the world many injuries still result from falling bullets. Even some cities in America have a problem with this, quite illegal, practice. In some parts of Latin America there are even more guns and fewer police available to try and halt the joy bullets. Because there are relatively few injuries from joy bullets (compared to fireworks) the dangers from falling bullets tends to be given little publicity. That is changing but slowly.
What probably made more people aware of this problem was the heavy losses from these falling objects during World War II. This was because for the first time lots of anti-aircraft guns were used around densely populated urban areas in Europe and Asia. The result was thousands of casualties from what were, at first, mysterious metal objects falling silently from the sky. The British later estimated that some 25 percent of civilian casualties from German World War II bombing attacks on their cities were from this sort of friendly fire. That is, British anti-aircraft shells eventually fell to earth and caused property damage and casualties.
Most of the civilian casualties from the Japanese attack on Pearl Harbor were from American anti-aircraft shells and bullets falling back to earth. A lot of the anti-aircraft guns used to defend Pearl Harbor were .50 caliber (12.7mm) machine-guns, and these bullets will kill you if they drop on your head and injure you if they hit any other body part. A .50 caliber bullet weighs about 50 grams (nearly two ounces). This is much heavier than rifle bullets, which will also kill or injure you if one drops on your head and hits the right spot. Kids are more vulnerable to this sort of thing. Shell fragments often weigh a kilogram (several pounds) and have sharp edges as well.
In Iraq, during the 1990s, there were instances of anti-aircraft missiles falling back to earth intact inside cities or towns. Since these things weigh several tons, they hit like a bomb. Normally the missiles are supposed to self-destruct (explode) if they don't find a target, and even if they do that is still thousands of fragments that fall back to earth. Some of these missile pieces weigh five kilograms (11 pounds) or more. Get hit by one of these and you are dead. Large objects coming down will damage buildings and vehicles. Most explosions, be they roadside bombs, smart bombs, artillery shells, or missiles, toss heavy objects into the air. This stuff comes down somewhere and if someone is in the way they become a casualty. Whose casualty is largely a matter of who gets the more convincing press release into circulation.
In some parts of the world a massive use of fireworks in a short period of time can cause another problem: black powder smog. These huge clouds of unhealthy explosives residue suspended in the air can be so bad that local airport operations have to be suspended for a while. In some areas, the manufacture of fireworks is unregulated (not by design) and some of the amateur rockets and such contain a kilogram (2.2 pounds) or more of black powder. Fortunately, black powder is a slow burning and not-very-powerful explosive, so terrorists generally avoid it. Industrial and military explosives are much more effective at killing people. But, in a pinch, some of that fireworks grade black powder will do.
What goes up must come down, often with calamitous effect.