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included the expanding knowledge and measurement of airway pollution and the connection
between higher or longer duration of daily exposure and increased cardiovascular and
respiratory mortality and morbidity. Through the 1990s increasing effort was made to clarify
the effects of the different pollutant components. Particulate matter, especially respirable
particles at less than l0 microns in diameter, and ozone have been consistently associated
with excess disease and mortality. However the nitrogen oxides have also had associations
with increased respiratory disease (bronchitis, COPD, pneumonia and asthma) and for more
episodes of wheeze with increased symptoms and lower lung function in adults and children
with asthma.
The second area led from the startling discovery of the gas NO as a ubiquitous, biological
messenger acting as a physiological mediator, a neurotransmitter and a mechanism of host
defence. Since this was realised, research into NO in every biological system flourished.
However there were a number of hurdles to overcome in measuring this molecule. Measuring
NO was going to be difficult given its gaseous, short lived and highly reactive nature, and
there were also the difficulties of measuring levels in exhaled air from human subjects.
In 1992 NO was named Science Magazine's "Molecule of the Year". In 1998 Robert F.
Furchgott, Louis J. Ignano and Ferid Murad were winners of the 1998 Nobel prize in
Medicine for their research in identifying firstly EDRF, and then renaming and identifying
NO as the mediator in vascular epithelium.
The following chapter will discuss the synthesis and control of NO production in detail, the
interactions of NO with other chemical and biological compounds, and the synthesis and
control of the nitric oxide synthase enzymes that produce it. This knowledge is preparatory to
discussing how to measure No concentrations in the respiratory system.
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