Breath of Fresh Air: Feature Articles

It would seem that we all have enough to worry about simply managing our asthma and other affairs on a day-to-day basis without having to add more worries about the environment. However, use of many of our most common asthma medicines links us to a global environmental issue: depletion of the ozone layer in the upper atmosphere. As a result, over the next several years we will be seeing changes in the way our inhaled asthma medications are delivered.

Ozone is a molecule composed of three oxygen atoms. When it builds up at ground level as part of heavy summertime pollution, ozone can worsen our breathing. But most ozone accumulates high in the atmosphere miles above the surface of the earth, and there it provides an important and beneficial service. It helps to screen out hamful ultraviolet radiation before it reaches us and other living creatures at the surface of the earth. Approximately twelve years ago [in approximately 1985], it was discovered that this protective layer of ozone was becoming thinner. It was especially noted in the springtime over the Antarctica, where an enlarging "ozone hole" was observed.

Less ozone protection against ultraviolet radiation means greater risk for cataracts and skin cancers. It also affects plant life and growth of sea plankton and so, if not reversed, may impact on the entire food chain.

The protective layer of ozone in the upper atmosphere is getting thinner.

Also approximately 12 years ago, evidence was already available that man-made chemicals released into our atmosphere are the cause of the ozone depletion. An especially important cause of destruction of the ozone layer is a group of chemicals called chlorofluorocarbons or CFCs. Developed in the 1930s, CFCs are widely used in refrigeration units and air conditioners (for example, freon is a CFC). It is also used as an aerosol propellant.

Here is where asthma comes into the picture. A small percentage of all manufactured CFCs are used to propel the sprays from our medication inhalers, the metered-dose inhalers or MDIs. Most of the inhaled bronchodilators and inhaled antiinflammatory medications that we use to treat asthma are delivered from pressurized canisters that utilize CFCs as propellants. Lest we feel too guilty, remember that less than 0.01% of all CFCs that enter the atmosphere come from our asthma inhalers.

Man-made chemicals destroy the ozone layer, especially CFCs such as are used as propellants in our metered-dose inhalers.

In response to this environmental problem, more than 130 countries came together under the auspices of the United Nations to sign an agreement -- known as the Montreal Protocol -- to eliminate production and use of CFCs by the year 2000 [now extended to the year 2005[??]. Where does that leave persons with asthma and related lung diseases?

Two alternatives to CFC-propelled MDIs are becoming available. One involves the development of alternative chemical compounds that act as propellants but do not destroy ozone. One such group of chemicals are the hydrofluoroalkanes (HFAs), and already one bronchodilator (the Proventil® brand of albuterol) is available with this ozone-safe propellant (Proventil-HFA®).

The other approach is development of medication delivery systems that are driven not by chemical propellants but by our own inhalation. Medications contained within their canisters in the form of a dry powder can be made into aerosols by the force of a strong breath in. These so-called "dry-powder inhalers" are widely used for asthma medications in Europe and will likely soon be introduced in the United States. One medication currently is available in a similar form. Albuterol comes as a dry powder within gelatin capsules (Ventolin® Rotacaps®), one dose per capsule, and can be delivered without propellants from a Rotahaler® device. The disadvantage of this particular system is that each medication dose needs to be carried as a separate capsule. Future dry powder inhalers will contain more than one hundred doses of medication in dry powder form within each canister.

[Editor’s note: Two multi-dose dry-powder inhalers are currently available. One device delivers an inhaled steroid, budesonide, and is called a Pulmicort® Turbuhaler®. Its mechanism is shown in the accompanying illustration. The other device delivers the long-acting bronchodilator, salmeterol. It is called Serevent® Diskus®.]

Alternative, CFC-free inhalers are now becoming available:

One form is a traditional metered-dose inhaler with a new, ozone-safe propellant.

The other form is a dry-powder inhaler, where an aerosol is made by the force of one’s breathing in.