Edinburgh Napier University

  Epidemiological studies have reported that ozone-pollution has a negative impact on human health. This pollutant is associated with high temperatures and is expected to continue to rise with the predicted global warming. People and athletes that exercise outdoors are of particular concern because, the more intense and the more prolonged the activity, the higher the ozone dose delivered to the lungs and potentially the higher the risk for performance impairment, lung function decrement, onset of lung inflammation, lung injury and oxidative stress.

The main aim of the studies contained in this thesis was to evaluate the impact of ozone-pollution (0.1 ppm), heat and humidity on well trained runners taking part in an 8 km time trial run. Different end points were investigated for an analysis of the impact on performance outcome, lung function, lung inflammation and oxidative stress. In addition, a second aim was to investigate whether a 2-week supplementation period of vitamin C (500 mg•day-1) and vitamin E (100 IU•day-1) would provide any beneficial effects to the participants.

The participants’ lung function was measured by spirometry. Lung inflammation and oxidative stress status were assessed by a variety of markers both in the upper respiratory airways, by nasal lavage, and in the plasma. The markers assessed included: neutrophil count, clara cell protein (CC16), interleukin-8 (IL-8), uric acid, GSH/Protein and trolox equivalent antioxidant capacity. The results showed that the athletes performance was significantly decreased in the hot and humid condition (mean ± SD: 32min 35sec ± 2min 25sec) and in the hot, humid and ozone-polluted condition (33min 09sec ± 2min 44sec) when compared with the ozone alone condition (30min 27sec ± 2min 23sec) and the control condition (30min 15sec ± 1min 58seg). Ozone alone had little effect on the performance variable. The participants’ lung function was not affected by the adverse environmental conditions. Evidence of early lung epithelial injury, however, was observed by an increase in CC16 in the upper respiratory airways immediately after the exercise trial in the hot, humid and ozone-polluted environment; though this was not observed for any other marker of inflammation at this time point. In this same adverse environmental condition, an increase in the GSH/Protein concentration in the upper respiratory airways was found immediately after the exercise.

It was observed that the 2-week supplementation protocol improved the runners’ time to complete the 8 km time-trial run in the hot, humid and ozone-polluted environment by 2.6%. In addition, the supplementation was shown to be effective in decreasing the lung inflammation induced by the combination of ozone pollution, heat and intense exercise. This was observed by a smaller increase in the concentration of CC16 in both the upper respiratory airways (0.67 ± 0.5 mg•l-1) and plasma (39.4 ± 17.4 ng•ml-1) in the vitamin treatment compared to the placebo. In addition, in the vitamin treatment the, cortisol concentration (29.2 ± 14.8 ng•ml-1) after the run, the IL-8 concentration (75.8 ± 43.2 pg•ml-1) and neutrophil percentage (22.6 ± 17.2 %) in the airways 6 h after the run were also reduced compared to the values in the placebo treatment (49.9 ± 13.4 ng•ml-1; 126.6 ± 103.2 pg•ml-1; 25.2 ± 22.6 % respectively).

Taken into consideration together, these results provide evidence that heat and humidity combined with ozone have a detrimental effect on athletes’ performance in an 8 km time trial, it cannot be discounted that this was simply due to the heat and humidity as there was no differences in the two heat performances. The hot, humid and ozone environment elicited an early epithelial damage characterized by increase in CC16 concentration in the airways. Moreover, an increase in the antioxidant concentration in the upper respiratory airways in that same trial, as indicated by the nasal lavage GSH/protein, suggests a protective mechanism against the oxidative stress stimulated by the high intensity exercise in association with ozone, heat and humidity. Heat and humidity alone had a similar detrimental effect in performance. While, ozone alone had little effect on the variables. In addition, it can be suggested that 2 weeks of a low dosage of vitamin C and E supplementation might present some benefits for the performance outcome and immune system of trained individuals when taking part in a running competition in an ozone-polluted, hot and humid environment. These benefits will, however, depend on the regulation of the antioxidants uptake and metabolism of each subject.