Global Lead Network: Don't Repeat the Leaded Gasoline Experiment: Keep MMT Out of Gasoline
Don't Repeat the Leaded Gasoline Experiment: Keep MMT Out of Gasoline
Background Paper and Policy Statement
Background: Countries on the verge of phasing out leaded gasoline are faced with a myriad of choices for replacement fuels. Optimally, governments will take advantage of the opportunity pre-sented by phase-out to implement an integrated clean fuels strategy that will protect public health, re-duce conventional pollutants, and combat climate change. Unfortunately, a small number of countries have chosen to replace lead with another metal-based additive, methylcyclopentadienyl manganese tricarbonyl (MMT) – and the trend is growing. While the switch from tetraethyl lead (TEL) to MMT will by definition reduce lead pollution and poisoning, the use of MMT opens a Pandora’s box of other problems.
The history of MMT thus far largely mirrors that of TEL. When TEL was first introduced to gasoline in the 1920’s, the long-term effects of low-level exposure on public health were unknown – as is the case with MMT today. Now the verdict is in – leaded gasoline has been proven a disastrous “experi-ment.” The long-term and efficient dispersion of this persistent elemental neurotoxin into the envi-ronment has left a legacy of environmental contamination, impaired human potential, and enormous social costs.
The company that manufactures and markets MMT around the world, the Ethyl Corporation, is the same company that brought us TEL – and insisted for decades that lead from automobile emissions was not a significant source of exposure and was not dangerous to health at low levels. Today, Ethyl uses these same arguments to promote MMT use. Ethyl claims that MMT is the most-studied gasoline additive in history and that there is no proof that manganese damages health, the environment, or automotive performance. Unfortunately, the reverse is also true – there is no proof that MMT does NOT damage health, the environment, and automotive performance. In essence, Ethyl is asking us to repeat the large-scale human experiment of TEL by exposing millions of people to a known neurotoxin and waiting to see what ill effects occur.
In fact, the evidence we do have is cause for concern. Studies of workers exposed to airborne manga-nese show that when manganese is inhaled, it can cause Parkinson’s-like symptoms, including tremors, slowed reaction times, and difficulty learning. Furthermore, various automobile and emission control technology manufacturers have conducted studies demonstrating that MMT use interferes with cata-lytic converter performance, increases emissions, and reduces fuel economy. Thus the introduction of MMT could negate the broader positive results of leaded gasoline phase-out – improved air quality and climate change mitigation.
The use of MMT is a classic case where scientific evidence proving its safety to human health and the environment should be required before its introduction. This action would prevent introducing a po-tential neurotoxin into a very efficient delivery system, automobiles, without first proving that MMT will not cause harm.
Before MMT is adopted as the substitute of choice for lead, there are a variety of important questions that need to be answered, including:
- Which manganese compounds are primarily emitted from the tailpipe: manganese oxide, manga-nese phosphate, or manganese sulfate? What is the particulate size of manganese-containing emis-sions? And how do differences in compounds and particulate sizes affect health outcomes?
- What are the effects of exposure to low levels of airborne manganese or manganese compounds over a lifetime?
- Are certain segments of the population, such as fetuses, children, and the elderly, particularly vul-nerable?
- What are the effects of MMT on automobile performance and emission control systems?
Why should lead poisoning prevention, climate change, and clean air advocates care about MMT? Most importantly, we cannot declare victory over leaded gasoline if lead is replaced with another ele-mental neurotoxin. Leaded gasoline phase-out is vital to protecting public health and the environment not only because it prevents exposure to lead, but because it is a prerequisite to introducing catalytic converters, oxygen sensors, and other pollution control and energy-saving devices. Replacing lead with MMT represents a lost opportunity to improve air quality and vehicle performance.
We are still paying the price for the 80-year (and counting) TEL experiment. Millions of adults and children continue to be exposed to airborne lead emitted from tailpipes. Even in those countries where leaded gasoline was banned long ago, a reservoir of lead remains in the environment and will ulti-mately have to be addressed. We cannot afford to have more generations robbed of their futures as a result of daily and involuntary exposure to a neurotoxin.
Policy Statement: Urgent Need to Apply the Precautionary Principle to MMT Use
- First and foremost, countries should honor their commitments to phase out leaded gasoline as soon as possible, and certainly no later than 2005.
- Countries should implement commitments to phase out leaded gasoline in the context of an inte-grated clean fuels approach: sharply reducing sulfur content and guarding against additives, such as MMT, that do not improve environmental protection and public health and that hinder pollution control and performance.
- Full information and data regarding the production and use of MMT and other additives should be made transparently available.
- Countries that already have introduced MMT should immediately begin to eliminate it. During the transition period, gasoline containing MMT should be clearly labeled at the pump and the public should be warned of its potential dangers.
- Countries should resist introducing MMT and any other ash-forming additives until definitive stud-ies carried out by disinterested parties have proven their safety. Likewise, other additives should be proven safe before they are introduced as replacements for TEL. This includes additives that indirectly affect the environment and health through their interference with pollution control equipment and fuel efficiency, thus making it impossible to reach broader goals of reducing emissions of conventional pollutants and greenhouse gases.
* For more information, see the Alliance’s MMT Fact Sheet.
