Deborah Blum at Speakeasy Science has put up a terrific two-part post about the early history of leaded gasoline, which bears much of the blame for lead poisoning in workers and the general population. (Paint containing lead is the other main culprit.) Blum's "At the Door of the Loony Gas Building" and "Of Dead Bodies and Dirty Streets" involve plot developments that might sound familiar: product kills people, industry insists product is safe, and back-and-forth about product's safety continues for decades before the product is finally altered, eliminated, or restricted to reduce harm to public health.
In the US, there's some good news at the end of the story, although it's not entirely happily-ever-after.
Sales of leaded gasoline started dropping off in the mid-1970s, after EPA set emissions regulations that prompted car companies to turn to catalytic converters, which don't work well with leaded fuel. Researchers from CDC's National Center for Environmental Health and Harvard University's School of Public Health studied the decline in blood lead levels between 1976 and 1999 and calculated what the BLL drop meant for IQs. Here's what they found:
These calculations imply that, because of falling BLLs, U.S. preschool-aged children in the late 1990s had IQs that were, on average, 2.2-4.7 points higher than they would have been if they had the blood lead distribution observed among U.S. preschool-aged children in the late 1970s. We estimated that each IQ point raises worker productivity 1.76-2.38%. With discounted lifetime earnings of $723,300 for each 2-year-old in 2000 dollars, the estimated economic benefit for each year's cohort of 3.8 million 2-year-old children ranges from $110 billion to $319 billion.
While this is something to cheer, it's also frustrating that widespread lead poisoning continued for so long after the 1920s, when lead's role as a neurotoxi
ncant was well known. The continued use of lead well into the 20th century not only affected those who suffered its harmful effects during that time period, but allowed for the buildup of contamination that's still affecting children today. CDC reports, "Approximately 250,000 U.S. children aged 1-5 years have blood lead levels greater than 10 micrograms of lead per deciliter of blood, the level at which CDC recommends public health actions be initiated." Old, peeling paint and contaminated dust are the main sources of exposure today, and many cities (particularly those with older housing stocks) find it difficult to fund the rehabilitation that would further reduce lead exposure.
The profits from the continued sale of leaded gasoline were concentrated among a small group of people, but the costs were spread across the population. The oil refinery workers described in Blum's pieces, who were severely -- in some cases, fatally -- poisoned, paid the most dearly. Lead-poisoned children and their families have borne the burdens related to learning and behavior problems. The US as a whole has lost billions of dollars worth of worker productivity.
Lead might seem like a closed chapter in US history, but that's not the case at the global level. In many developing countries without regulatory systems that effectively limit lead exposures, the costs of lead poisoning are mounting.
I've had some interest in lead, and it is amazing. I think it must be one of the biggest unsung denialism stories ever. Bigger than cigarettes even. And it is still ongoing too sometimes, just in the washington DC 2006 water crisis the city changed the water chemistry and it started releasing vast amounts of lead from lead plumbing, and the EPA published fraudulent studies in an attempt to make their jobs easier/cover their behinds.
If you buy a roll of solder, there is a big warning about the ammonium hydrochloride (which is edible, added to candy in the UK in the 2% range) but just a little caution symbol about lead. So people still use it on plumbing, I read once (can't find it again now) it is estimated that 30% of brand new houses still have at least one lead solder sweat joint because worker do not know it is toxic. There have been several cases of full blown lead poisoning (the joints release a lot more lead soon after they are fist done), including a case report of a father and son that were hospitalized because they drank water - dun dun dun - straight from the tap.
BTW tetraethyl lead is *still legal and for sale* for use with off road vehicles of all sorts. Lead paint is no longet used for *interior* paint, but in industry it is still the norm for exterior paint on bridges etc.
I once saw a geotechnical survey of soil and dust in houses (done in 1998) and it actually contains a remarkable amount of lead still, most of it is thought to be from tetraethyl lead which has been converted to insoluble sulfide from acid rain, and thus never washed away. It's like 1 mg/g IIRC. I don't know how many people still live in houses that have lead paint but it is a lot. BTW given the half life of lead in blood (30 days) and the amount that gets absorbed, (bout half) and the amount of blood in a child (I forget exactly I think it is like 6 liters) you can calculate how much you need to ingest daily to get 10 micrograms per deciliter of blood. It's tiny. I forget exactly but it's like 20 micrograms, and the real question becomes why isn't every one poisoned.
Liz, you appear to be blocking legitimate comments, on purpose or no.
Great post, will be retweeting this. Let everyone know about the costs of lead poisoning.
Ed, ScienceBlogs gets a lot of spam and has pretty strong comment filters. If people find their comments aren't showing up, I generally recommend excluding URLs and keeping the comments short.
Technically, lead is a neurotoxicant, not a neurotoxin.
Good catch, Justin, thanks! (It's fixed now.)
For those not aware of the distinction, a toxin is something produced by a living organism - so, bacteria produce toxins (like the botulinum neuroxin), but metals and synthetic chemicals do not.
Sorry to hijack your thread, but here's something I thought you might want to see. Not surprisingly, in the comments there is a response from the fragrance industry.
Nice Try, Dr. Borkowski. All the other science bloggers have access to the spam bin and have no such problems to begin with.
Ed, based on your last comment, I'm going to guess that you intended your initial comment as a request that I check the spam bin for your comment. I do have that capability, and I will look for it.
In general, I think it's good commenting practice to keep comments concise and avoid loading them with URLs. Which isn't to say I haven't left lengthy comments on others blogs, and they've sometimes gotten flagged as spam. Good advice for anyone who comments on any blog: if you're spending a lot of time composing a comment, save a copy in a Notepad (or similar) document - I learned this one the hard way.
Yep, lead is still in use for some applications, and still exists in a lot of older homes and infrastructure. Its use has been reduced enough in the areas that were responsible for a large share of exposure that we've been able to see a significant reduction in lead-poisoning cases.
As to why everyone isn't poisoned, I think a lot of that has to do with exposure route - lead might be present, but not necessarily in a form that's likely to give someone a concentrated dose. For instance, adults in homes with lead paint are much less likely to be ingesting paint chips than small children are.
Let's not forget America's favorite spectator-exposed marketing program veiled as a sports event: NASCAR, and the many levels of stock car racing--all with high octane leaded fuel. Gives new meaning to "lead-footed driver".
European and International race programs, under FIM rules--Formula 1, MotoGP motorcycles, and others, banned leaded fuel a long time ago. Sit in the bleachers of a mega-track facility with a few dozen five mile per gallon lead burners going road and road for hours, and you can skip the paint dust at home. Truck and tractor pulls indoors are even worse.
And there's the huge specter of American aviation--all the piston-driven small planes and helicopters in commercial and private aircraft are still burning leaded fuels. Seems living near a small airport is now correlated with high lead levels from all the aerosolized PM-10 particles drifting about.
And don't forget the lead arsenate in legacy orchards and farms--used through the 1960s--and some orchards, like Barber Orchards in Hendersonville, NC, as an example--are Superfund sites. Stripping the top foot of soil from 80 acres of the old apple orchard--now a subdivision--is a $15 million project. Seems lead is being made into gold, where the harmed have some influence on government spending. For most, it's just a life of diminished potential.