theonomist writes:
Leaded gasoline is still widely used in so-called "third world" countries, with no apparent ill-effects yet reported. Vague talk about "researchers suddenly and violently dying" is of course meaningless. ... I see no references. ... The dangers of lead are imaginary.
Oh really? Let's investigate that for a moment. A quick search on PubMed revealed the following articles:
  1. Shen X, Rosen JF, Guo D, Wu S., Childhood lead poisoning in China, Sci Total Environ 1996 Mar 15;181(2):101-9

    This is a study from China. The authors studied blood level concentrations of young children in rural areas and major cities (Shanghai, Shenyang, Fuzhou and Beijing), and related this to health effects that were observed. Quoted from the abstract:

    The link between low-level lead exposure and deficits in IQ, neurobehavioral development and physical growth is remarkably consistent without exception. In summary, the harmful health effects of childhood lead poisoning in limited studies of exposed and 'unexposed' children demonstrate that this totally preventable disease warrants considerable public health attention in China.
  2. Manay N, Pereira L, Cousillas Z., Lead contamination in Uruguay, Rev Environ Contam Toxicol 1999;159:25-39

    This paper from Uruguay investigates the blood lead concentrations in young children. The reported health problems with young children are related to heavy traffic with cars that are still fueled with leaded gasoline.

  3. Srianujata S., Lead--the toxic metal to stay with human., J Toxicol Sci 1998 Jul;23 Suppl 2:237-40

    This is a paper from Bangkok, Thailand. Quoted from the abstract:

    The well-known and excessive environmental exposures are air of industrial and heavy traffic areas. Use of leaded gasoline has caused the main lead pollution for years in almost every big city. Therefore, city inhabitants normally exposed to lead much more than those who live in the rural area. The most vulnerable groups at risk to lead exposure are fetuses and preschool age children. Young children in the 2-3 year-old age may be the most at risk for exposure to contaminated soil. Adults are affected when exposure is excessive in the working place and causing lead poisoning. Toxicities are mainly on heme biosynthesis, neurological effects including encepharopathy, peripheral neuropathy, and most importantly on I.Q. deficits. It also affects renal tissues to produce acute and chronic nephropathy and elevated blood pressure. There are studies of lead exposure of various means and the effects on human health, both in children and adults.
  4. Caprino L, Togna GI., Potential health effects of gasoline and its constituents: A review of current literature (1990-1997) on toxicological data., Environ Health Perspect 1998 Mar;106(3):115-25

    This Italian paper reviews toxicological studies (experimental and epidemiological) on the leaded and unleaded fuels, as well as their components and additives. It addresses the difficulties in assessing health effects from leaded gasoline independent from extraneous factors, and the advances that have been made with respect to this issue.

  5. Romieu I, Palazuelos E, Hernandez Avila M, Rios C, Munoz I, Jimenez C, Cahero G., Sources of lead exposure in Mexico City, Environ Health Perspect 1994 Apr;102(4):384-9

    This Mexican paper concludes that leaded gasoline is one of the major sources of lead poisoning, and it investigates the health effects on the Mexican population.

  6. Vega J, Contreras A, Rios E, Marchetti N, Agurto M., Lead exposure and its effects on child health, Rev Chil Pediatr 1990 May-Jun;61(3):154-60

    This Chilean paper lists several health effects of lead poisoning: Neurological symptoms (hyperactivity, distractibility, lower intellectual development), psychological difficulties (behavioral deficits), hematologic abnormalities (reduction in the biosynthesis of heme, anemia), and metabolic changes (reduction in concentration of 1-25 dihydroxy vitamin D and in the metabolism of erythrocyte pyrimidine). Prenatal exposure to lead may be related to minor congenital abnormalities, tumors of the kidney, and growth abnormalities.

  7. Hadnagy W, Seemayer NH., Genotoxicity of particulate emissions from gasoline-powered engines evaluated by short-term bioassays, Exp Pathol 1989;37(1-4):43-50

    A German paper listing the genotoxic and cytotoxic effects of both leaded and unleaded fuel.

I only included literature from recent years (1989-1999), but the effects of low level lead poisoning have been known for many decades. In fact, the earliest studies were done only a few years after the discovery of tetra ethyl lead as an anti-knock agent (around 1922). As you can see, most of the current literature contributions on lead poisoning come from countries that still use leaded gasoline, or to quote theonomist: ' "third world" countries, with no apparent ill-effects yet reported'

theonomist continues:

Fact: A long-term study (the Harris-Martin-Rex Effluent Impact Study) conducted by the United States Department of Agriculture in the 1960s and 1970s accumulated overwhelming evidence indicating that fumes from leaded gasoline had no adverse effects on small mammals (mice, rats), nor any on insects...

So the only rebuttal to the overwhelming amount of literature proclaiming the dangers of lead poisoning is ONE report from the sixties, that wasn't published in any peer-reviewed journal? theonomist wonders why that study is never mentioned anywhere, and blames it on liberal "environmentalist hysteria".

Of course, it could be a mass environmentalist conspiracy, but I tend towards Occam's Razor. Maybe the Harris-Martin-Rex Effluent Impact Study is never mentioned anywhere because it is utterly wrong. But who knows what the results of the Harris-Martin- Rex study is all about; the United States Department of Agriculture doesn't have this report listed anywhere, and it doesn't show up anywhere in any scientific citations.

Another point that needs to be made from the theonomist's summary of the Harris-Martin-Rex study is that it (apparently) only studied small rodents and insects. Extrapolation of test results with animals to humans has to be done with extreme care, and sometimes conclusions that can be drawn from laboratory animals are in no way valid for larger animals or humans. This seems especially true for the long-term health effects associated with lead poisoning; rodents simply don't live long enough to observe these effects. Also, I'm pretty curious to how you would conduct an I.Q. test on a rat to show that there are no intelligence deficits as was found in human babies suffering from lead poisoning.

But let's conclude with some insight to the sudden change of leaded fuel to unleaded fuel. In the 1970's and early 1980's there was an increasing drive to cut exhaust emissions from automobiles. The major focus of the government has been to cut the emissions from unreacted hydrocarbons, the toxic carbon monoxide, and nitrogen oxides (NOx); a major contributor to acid rain. Research has led to the development of a so called three-way catalyst, that is capable of reducing emissions of all of the above mentioned pollutants. The only problem is that lead reduces the catalytic activity by irreversibly reacting with the catalyst surface. In order to make this technology work, the gasoline had to be lead-free.

As mentioned before, the health risks of lead to humans were already known for a long time, but this by itself would not have been enough to change the market. Also, there needed to be an alternative to lead as anti- knock agent. The oil industry found a replacement called MTBE, Methyl Tert-Butyl Ether. This compound had the added advantage that it is an organic additive, instead of a metal, and thus could be synthesized from petroleum products. This meant that the oil companies could make additional profit on unleaded gasoline. This may explain why oil companies were none too hesitant to remove lead additives from gasoline.

lordaych: You are absolutely right that MTBE has proven to be a poor substitute for lead. This is due to its high solubility in (ground) water, and as you mentioned, the low detection threshold.

Many alternatives for MTBE have been proposed including tertiary butyl alcohol (TBA), ethyl tert-butyl ether (ETBE), tert-amyl ether (TAME), methanol, and ethanol. Ethanol appears to be the most promising, but the oil refineries are reluctant.

Ethanol is indeed an excellent oxygenate; better than MTBE, and only slightly worse than the toxic methanol. However, ethanol has a relatively high (Reid) vapor pressure. The vapor pressure of fuels is regulated to obtain proper combustion characteristics in the engine. Therefore, the switch from MTBE to ethanol isn't a simple switch: the entire fuel composition needs to be reformulated. It's not an impossible task, but oil companies don't like a lot of change.

Bio-ethanol is an environmentally friendly product but not really cheap; it requires distillation to achieve near 100% purity (this is actually quite involved due to the ethanol-water azeotrope). Cost estimates (CA Energy commission) predict an initial added price of 6.1 - 6.7 cents per gallon. It is reasonable, but it's not a great selling point towards the consumer that already thinks it is paying far too much at the pump. Furthermore, ethanol has a lower energy content, resulting in a slightly lower fuel economy.

I'm sure you meant the comment on Uranium dust in jest, but burning it in the air is a bad idea. The radioactive decay of Uranium leads to several isotopes of: ...Lead.