A handbook of environmental toxicology: human disorders and ecotoxicology.

Chapter 5 (Page no: 75)

Ozone I. Human disorders: an overview.

Ground-level ozone is one of the most widespread pollutants in the world. Millions of people are exposed to unhealthy levels of ozone air pollution on a daily basis. Often called 'smog', ozone is harmful to breathe and is associated with the development and exacerbation of pulmonary and cardiovascular disease. Scientists have studied the effects of ozone exposure on human health for decades. Hundreds of research studies have confirmed that ozone harms the human body when inhaled at levels currently found in many cities and countries. Ozone is a gas molecule composed of three oxygen atoms that is formed by a reaction between atmospheric oxygen and organic volatile compounds from vehicle and industrial emissions in the presence of sunlight. When inhaled, ozone aggressively attacks lung tissue and triggers systemic inflammation that can result in a series of health complications, ranging from inflammation and injury of the airways to alterations of vital functions at the cardiovascular, immune, endocrine and neurological levels and even death. In women, exposure to ozone can also affect fertility, cause pregnancy complications and alter fetal development. It has also been noted that susceptibility to ozone varies with age, gender and health status and studies have indicated that sex hormones can contribute to the damaging effects of ozone in the lung. Patients suffering from inflammatory lung disease, including asthma, bronchitis, chronic obstructive pulmonary disease and lung infection, are at significantly higher risk for negative health effects associated with ozone exposure. Numerous studies in cells and animal models have helped to elucidate some of the mechanisms of ozone toxicity and have identified cell receptors and inflammatory cytokines that activate the inflammatory response upon ozone exposure. These have also provided information for environmental agencies to control emissions and warn the population about unhealthy levels. In this chapter, we summarize the known effects of ozone exposure on human health, as well as the main results from clinical and animal studies testing ozone exposure at different doses. We also discuss current policies and regulations aimed to control emissions and potential harm to various populations. A better understanding of the negative effects of ozone exposure on human health and of the mechanisms associated with its toxicity will likely inform policy makers to introduce new guidelines to control environmental emissions and will allow for the development of strategies for symptom management and potential therapeutics for different individuals exposed to unhealthy ozone levels.

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