I was surprised recently to learn that general aviation aircraft still use leaded fuel. I wonder how much lead we are all still exposed to because of this? Is there some technical reason why it can't be removed?
If you think leaded avgas is bad (it is), wait until you learn about lead-based stabilizer compounds in PVC (which is used in electrical cables and pipes/hoses, among other things). Those compounds aren't even chemically bonded with the actual PVC molecules, so the lead eagerly leaches out. Also there's lead in brass keys and in brass faucets (yes, even the ones marked "lead free", when it comes to potable water piping/fixtures, "lead free" actually means "0.25% lead").
AFAIK there's no regulation in US that will force reformulation with lead-free compounds (which do exist), the best the US has is California's Prop 65, which provides a bunch of useless labels which people are trained to ignore. What a disaster.
> when it comes to potable water piping/fixtures, "lead free" actually means "0.25% lead"
It's a fucking farce that any lead is ever allowed to be purposely added to plumbing materials labeled "lead free". However, nowadays most such labeled materials actually are lead-free. All the big brass suppliers -- Concast, Chase, Viega, Mueller, others -- produce actual lead-free brass and bronze, with no more than trace and incidental amounts of lead.
> AFAIK there's no regulation in US that will force reformulation with lead-free compounds
Correct, nothing nation-wide, although companies that sell stuff to the EU often make RoHS/REACH compliant lead-free products for all markets, simply as a matter of efficiency.
You're also right, Prop 65 is a great example of smart and necessary idea that was crafted into a useless law. Labels without any actual market restrictions are an invitation to gaming by manufacturers, and apathy by consumers.
I also did not know this, so went digging. Looks like it's just small prop aircraft that still use leaded gas, even though most of them would run with unleaded just fine. How crazy!
Only newer engines can run unleaded. Most AV motors are made in the legacy style and have unhardened valve seats, requiring TEL in AVgas. Overhaul to mill the heads to install hardened seats would run 8k to over 100k depending on the craft. FAA only regulates when accidents happen it seems, so perhaps reframe the problem. FAA regs requiring proven engines and disincentivising things like fuel injection, electronic ignition, and other staples of ICE efficiency and reliability. We are effectively stuck in the 1950s in small aircraft ownership as a direct result. Considering the advancements, its a bit insane not to at least allow new tech, much less disincentivise it.
Another alternative would be coming up with some organometallic that replicates the properties of TEL, the transition metal(s) of which are something that's not lead. Or mercury, uranium, cadmium, and a few others that are really easy to avoid. Materials chemistry has gotten lots better over the past hundred years, the meaningful development costs are only in validation testing. The FAA "should" be able to cover that cost instead of individual pilots converting their engines.
>Is there some technical reason why it can't be removed?
One reason is that alternative octane boosters can cause icing in carburetors and fuel injection systems, resulting in engines cutting out at low temperatures. Improvements in combustion chamber design have helped reduce the reliance on high octane fuel, so I expect the situation will gradually improve.
