Propellants environmentally friendly

Although AP is the most widely used oxidizer for composite propellants, it is not environmentally friendly, and results in acid rain and the hazard of ozone depletion. Also its exhaust signature leads to problems of detection and tracking... 

Although hydrocarbon aerosol propellants are relatively inexpensive, nontoxic, and environmentally friendly (since they are not damaging to the ozone layer and are not greenhouse gases), their use is limited by their flammability. While hydrocarbon propellants are primarily used in topical aerosol formulations, it is possible that butane may also be useful in metered-dose inhalers as a replacement for chloro-fluorocarbons. 

In summary, DPIs are a widely accepted inhaled delivery dosage form, particularly in Europe, where they currently are used by approximately 40% of asthma patients, for the delivery of medications used to treat asthma and COPD. They may find use in a much broader spectrum of diseases as targeted delivery to the lung begins to be more widely accepted. Their lack of propellants makes them a desirable, environmentally friendly alternative. 

The pressurized metered dose inhalers in the use of environmentally friendly propellants means the choice of hydrofluoroalkanes, wherein the dosage form can be a suspension of the solution form. The problems of formulating suspensions, as discussed earlier, apply here as well, but particularly with respect to interactions with the formulation components specific to pressurized inhaler systems. 

Timsina et al. (1994) have reviewed the use of DPIs for drug delivery to the lungs. Although pMDIs remain the most popular device for the delivery of drugs to the lungs, DPIs have certain advantages over them. For example, DPIs do not rely on the CFC or HFA propellant gases and hence are more environmentally friendly than MDIs. 

Periodate salts have seen some application in propellant formulations and their use as environmentally friendly oxidizers in pyrotechnic formulations has been reported [13]. In particular, Moretti, Sabatini and Chen have developed incendiary mixtures featuring periodate salts KIO4 and NaI04 that perform similarly to perchlorates but are less toxic [13]. Combined with the alloy magnalium (magnesium-aluminium, 1 1) as the fuel, these mixtures produce a bright flash of light. 

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