for human health and the environment. In particular, a 2013 risk assessment on MMT was undertaken by ARCADIS Consulting, following a methodology developed by the European Commission. This risk assessment was verified by an independent panel and found by the EU Commission to be compliant with their methodology. It concluded that “when MMT is used as a fuel additive in petrol, no significant human health or environmental concerns related to exposure to either MMT or its transformation [combustion] products (manganese phosphate, manganese sulphate and manganese tetroxide) were identified even in locations where MMT is approved for use at levels up to 18 mg Mn/L.” As stated by Health Canada in their risk assessment on the widespread use of MMT in Canadian gasoline, “all analyses indicate that the combustion products of MMT in gasoline do not represent an added health risk to the Canadian population” MMT is manufactured by reduction of bis(methylcyclopentadienyl) manganese using triethylaluminium. The reduction is conducted under an atmosphere of carbon monoxide. MMT is a so-called half-sandwich compound, or more specifically a piano-stool complex (since the three CO ligands are like the legs of a piano stool). The manganese atom in MMT is coordinated with three carbonyl groups as well as to the methylcyclopentadienyl ring. These hydrophobic organic ligands make MMT highly lipophilic, which may increase bioaccumulation. While the structure of MMT suggests lipophilicity and potential to bioaccumulate, comparison of bioconcentration factors (BCF) reported for plant and animal species in comparison to regulatory-based cutoffs (i.e., US EPA and EU REACH) indicates a low bioaccumulative potential of MMT. Figures 2 and 3 of the study (pages 182 & 184) shows the BCF plotted against time and illustrates the potential BCF of MMT. From these figures, the upper curve (A) demonstrates the 9-day MMT BCF plateauing at approximately 400 in plants and 200 in fish, with both values well below the Bioaccumulative / Very Bioaccumulative (B/vB) thresholds of US EPA, EU REACH and Environment & Climate Change Canada. A variety of related complexes are known, including ferrocene, which is also under consideration as an additive to gasoline. Ferrocene Ferrocene is the organometallic compound with the formula Fe(C5H5)2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds. The rapid growth of organometallic chemistry is often attributed