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Seasonal Rhinitis and Environmental Factors in Madrid

J Investig Allergol Clin Immunol 2019; Vol. 29(5): 371-377

© 2019 Esmon Publicidad

doi: 10.18176/jiaci.0368

Ozone levels are mostly higher in rural areas than in

cities. Ozone is degraded by NO, which is also involved in its

formation. This degradation occurs more often in cities than

in rural areas, because there is more NOx in cities. For this

reason, ozone concentrations are higher in rural areas than in

cities [27].

According to the review of evidence on health aspects of

air pollution in the REVIHAAP Project (Technical Report)

(2013) [28], the European threshold of 180 µg/m


for informing

the population may thus not be viewed as an effective threshold

value under which absolutely no one will experience any effect at

all. However, theWorld Health Organization (WHO) postulated

that the effects of concentrations lower than 200 µg/m


will be

limited in severity and will only prevail in less than 5% of

the total population [29]. Warning the whole population at

lower concentration levels is therefore not advised.As such, the

threshold values can be considered a sliding scale, and—albeit

somewhat artificially—it is possible to talk about amild response

at (hourly mean) concentrations of 180-240 µg/m


, a moderate

response at 240-360 µg/m


, and a severe response above

360 µg/m


[28,29]. The review concludes that a considerable

amount of new scientific information on the adverse health

effects of particulate matter, ozone, and NO


observed at levels

commonly present in Europe in recent years [28]. This new

evidence supports the scientific conclusions of the WHO air

quality guidelines, last updated in 2005, and indicates that, in

some cases, the effects occur at air pollution concentrations

lower than those serving to establish these guidelines [29].

Pollution particles also contain diesel exhaust particles.

At present, 70% of all particles and 90% of those <5 µm

(respirable particles) are produced from its combustion, which

induces important biological changes, such as a more marked



2 response [30,31].

The rising frequency of obstructive respiratory diseases

during recent years, in particular allergic asthma, can be

partially explained by changes in the environment, with the

increasing presence in the atmosphere of chemical triggers

(particulate matter and gaseous components such as NO



ozone) and biologic triggers (aeroallergens). Consequently,

measures need to be taken to mitigate the future impact of

climate change and global warming [32]. Over the last 50 years,

the earth’s temperature has risen markedly, likely because of

growing concentrations of anthropogenic greenhouse gas [32].

For this reason, it is important to emphasize to patients that

climate change is increasing exposure to allergens and suggest

what they can do to minimize their exposures and thus reduce

allergy and asthma symptoms, such as checking pollen levels

frequently. In Spain, patients can sign up for free alerts from

the Spanish Society of Allergy and Clinical Immunology

Aerobiology Network. For patients with asthma, it is important

to check ozone levels.


The effect of temperature and pollution (mainly ozone,

even at lower atmospheric concentrations than those

established in guidelines about its effects on health) could

contribute to the higher seasonal allergic rhinitis symptom

score observed in 2009.

We highlight the need to continue research into the impact

of these changes and into strategies and policies to reduce

greenhouse gas emissions and air pollution.


The authors declare that no funding was received for the

present study.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Previous Presentation

This study was presented at Simposio Internacional de

Aerobiología, Contaminación y Cambio Climático, 26-28

October 2017, Murcia, Spain.


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