Combined effects of air pollution and allergens in the city of Rome

Abstract

Urban green is an important aspect in the quality of life of citizens of modern cities. Nevertheless some ornamental plants cause allergic diseases in sensitive subjects that may be worsened by air pollution.

Studies on air quality are usually addressed to the evaluation of single substances and their specific effects: little is known about the cumulative effect that different pollutants may have on human health. Even less is known about possible combined action of traditional air pollutants with pollen and spores that have huge effects, in terms of allergies and asthma, on citizenship of the urban areas.

In this work the synergistic effect of PM₁₀, PM_2.5, NO₂, O₃ and airborne pollens (belonging to 4 taxa: Cupressaceae/Taxaceae, Graminaceae, Olea and Urticaceae) was studied in the city of Rome during six years (from 2010 to 2015).

For air pollutants, concentration values recorded by air-quality monitoring network of Rome were used. Pollens and spores data were detected by the Aerobiological Monitoring Centre of the University of Rome Tor Vergata. Effects on human health were evaluated on a group of 100 patients (aged between 4 and 18) by the Allergymonitor™^ã application that records daily symptoms of hay fever, bronchial asthma and the prescribed therapies.

Data collected in the medical record were processed by 2 different Symptom Medication daily Scores and compared with time series of air concentration of mentioned pollutants, pollen and spores.

Statistical analysis allowed highlighting when concomitant high levels of allergenic species and air pollution occur, the influence of meteorological parameters, of the flowering calendar, of taking drugs and how these aspects affect symptoms in patients.

Introduction

Atmospheric pollution, especially in urban areas, is, nowadays, generally considered an important risk factor for human health and the ecosystem, but the consciousness of its importance has gradually increased during the last decades, following the progress of scientific research.

The first Italian act on air pollution was the 1966 Anti-smog law n. 615 (IP, 1966), followed by the 1971 executive regulation (IG, 1971) which provided the first concentration limits in the ambient air for many substances.

The 1983 Decree (IG, 1983), updated in 1988 with the DPR n. 203 (IG, 1988), abrogated and replaced the previous law and introduced limit values (or air quality standards) and guide values.

To protect human health from acute episodes of air pollution, two 1994 Ministry Decrees established attention and alert standards for the same substances (IG, 1994a, IG, 1994b).

Specifically, the 25/11/94 Ministry Decree (IG, 1994b) introduced quality objectives for the, at time so-called, unconventional pollutants (PM₁₀, Benzene, Benzo[a]pyrene).

Finally, a 1996 Ministry Decree introduced specific reference levels for tropospheric ozone (IG, 1996).

In the late nineties was issued the European Framework Directive for air quality (EC, 1996) and then a number of daughter directives addressed to specific pollutants. All these directives were gradually transposed in Italy since 1999.

The current European Directives on ambient air quality are the 2004/107/EC (EC, 2004) and the 2008/50/EC (EC, 2008) and these were both transposed and merged in Italy by the 2010 D. Lgs. n. 155 (IG, 2010).

The European Union adopted the 2008/50/EC Directive on ambient air quality and cleaner air for Europe in order to protect human health and the environment, to combat emissions of air pollutants, to identify and implement the most effective emission reduction measures and set appropriate objectives for ambient air quality, taking into account WHO standards. This Directive introduced limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM₁₀ and PM_2.5), lead, benzene, carbon monoxide and ozone in ambient air, establishing the exchange of information and data from networks and individual stations measuring ambient air pollution within the Member States. The 2008/50/EC Directive lays down measures aimed at defining and establishing objectives for ambient air quality designed to avoid, prevent or reduce harmful effects on human health and the environment as a whole; assessing the ambient air quality in Member States on the basis of common methods and criteria; obtaining information on ambient air quality in order to help combat air pollution and nuisance and to monitor long-term trends and improvements resulting from national and Community measures; ensuring that such information on ambient air quality is made available to the public; maintaining air quality where it is good and improving it in other cases; promoting increased cooperation between the Member States in reducing air pollution.

In many cases limits and threshold values set by The EU Directive do not coincide with the World Health Organization’s reference limit values: WHO thresholds for human health protection are lower than those foreseen by the legislation and much of the urban population is still exposed at higher levels than these guiding values. In addition, research and international regulations on air pollution are still typical today for evaluations of the individual substances and their specific effects: little is known about the cumulative effect that more air pollutants, at high concentration levels in the same time interval, may have on human health.

Even less has been explored the possible combined action of traditional pollutants with the granulometric particle of biological particulate matter, about 10 μm or more aerodynamic diameter, consisting of pollen and spores, which increases the consequences in terms of allergies and asthma in the urban centres (D’Amato et al., 2007).

Likewise, the absence of legal limits that directly link certain concentrations of pollen or aerated spores and human health does not allow absolute assessments of air quality.

The onset of symptoms occurs when pollen concentration, reaches a defined value, called threshold; but this threshold varies not only from individuals but also in the same individual during the season. Severe asthma occurrence can be also triggered during thunderstorms in the pollen season (D’Amato et al., 2016), and thunderstorm asthma can affect individuals without prior asthma (Girgis et al., 2000; Lee et al., 2017).

Allergy sufferers respond subjectively to allergy. The severity of the symptoms depends not only on the pollen exposure, but also on specific factors of the allergic person such as lifestyle, IgE antibody level, sensitization and simultaneous exposure to other allergenic sources, the target organ clinical reactivity (eyes, nose, lungs). Scientific studies show that predisposed subjects have increased respiratory reactivity induced by air pollution and increased bronchial responsiveness to inhaled pollen allergens. Air pollution has been associated with hospital admissions for respiratory disease in cities all over the world (Medina-Ramòn et al., 2006). Atmospheric pollutants, particularly ozone, particulate matter and sulphur dioxide, have an inflammatory effect on the airways of susceptible subjects, causing an increase in epithelial permeability, easier penetration of pollen allergen in the mucous membranes and greater interaction with immune system cells (D’Amato et al., 2007). In addition, some air pollution components seem to have an adjuvant immunological effect on the synthesis of immunoglobulin E (IgE) in atopic subjects: for each increase of 10 μg/m³ of PM₁₀ the risk of hospitalization or first aid visits increases by 1.5% and to worsen asthma increases by 3% (Pope et al., 1999). Another study has highlighted that by crossing the data from the wastewater analysis of the average number of daily doses consumed in the city of Milan and those made available by the ARPA Lombardia it was possible to find a direct and statistically significant correlation between PM₁₀ and PM_2.5 levels and the salbutamol doses used, the active ingredient present in the drugs used to counter bronchospasm during asthma crisis. Each increase in PM₁₀ of 10 μg/m³ corresponds to a 6% increase in salbutamol dose employed by the Milanese population (Fattore et al., 2016).

In addition, atmospheric pollution can interact both with pollen, leading to an increase in release of antigens with modified allergenicity, both with particles carrying allergenic of plants; these particles can reach peripheral airways with inhaled air and induce asthma in sensitive subjects.