Environmental urban factors and the risingtrends in allergic respiratory diseases . Inother words airway mucosal damage and impaired mucociliary clearance induced byair pollution may facilitate the access of inhaled allergens to the cells ofthe immune system.Anumber of factors is likely to be important in the increasing prevalence ofrespiratory allergy and these factors include changes in childhood infections,the sealing up of homes, the food ingested, a lack of physical exercise andairborne materials. Two factors are required for the onset of allergicdiseases: sensitizing agents and genetically committed individuals, and variousstudies suggest that air pollution contributes to the facilitation of allergicsensitization of the airway in predisposed subjects and to the exacerbation ofsymptoms in already allergic subjects. Although the nature and concentration ofoutdoor pollutants vary from place to place, the most abundant in theatmosphere of urban areas are respirable particulate matter (PM), NO2and ozone. In general, the effects of air pollutants on lung function dependson the environmental concentration of the pollutant, the duration of exposureand the total ventilation of exposed persons.Exposureto ozone may increase the risk of sensitization to aeroallergens in predisposedsubjects and may enhance the airway responsiveness of already sensitizedsubjects by lowering the threshold concentration of allergen able to induce theappearance of clinical symptoms. Penetration of PM into the tracheobronchialtract is related to its size and to the efficiency of the airways defencemechanisms. The latter effect could contribute to explain the increase of casesof sensitization to pollen allergens in urban areas.As forthe health effects of air pollution in subjects living in polluted urban areas,it has been found, both in US and in Europe an association of dailyconcentrations of particulates and other components of urban air pollution (NO2and SO2) and daily mortality. The effects of DEP on IgE productionhave been studied both invivo and invitro. Environmental urban factors (air pollution and allergens) and the risingtrends in allergic respiratory diseases . Althoughthe nature and concentration of outdoor pollutants vary from place to place, themost abundant in the atmosphere of urban areas are respirable particulatematter (PM), NO2 and ozone. In general, the effects of airpollutants on lung function depends on the environmental concentration of thepollutant, the duration of exposure and the total ventilation of exposedpersons.Exposureto ozone may increase the risk of sensitization to aeroallergens in predisposedsubjects and may enhance the airway responsiveness of already sensitizedsubjects by lowering the threshold concentration of allergen able to induce theappearance of clinical symptoms.
Penetration of PM into the tracheobronchialtract is related to its size and to the efficiency of the airways defencemechanisms. The latter effect could contribute to explain the increase of casesof sensitization to pollen allergens in urban areas.As forthe health effects of air pollution in subjects living in polluted urban areas,it has been found, both in US and in Europe an association of dailyconcentrations of particulates and other components of urban air pollution (NO2and SO2) and daily mortality. The effects of DEP on IgE productionhave been studied both invivo and invitro. .theMediterranean area, southern California and other locations where there issustained photochemical pollution. Ozone can affect both the upper and lowerrespiratory tracts and epidemiological studies have demonstrated decrements inpulmonary function of both asthmatics and nonasthmatics associated with increasedlevels of ambient ozone. Hospital admissions are also increased followingincreases in ambient ozone. Exposure to ozone may increase the risk ofsensitization to aeroallergens in predisposed subjects and may enhance theairway responsiveness of already sensitized subjects bylowering the thresholdconcentration of allergen able to induce the appearance of clinical symptoms.Ozone induces inflammatory effects in upper and lower airways favoring themigration in nasal and bronchial mucosa of eosinophils, neutrophils, eosinophilperoxidase, myeloperoxidase, eosinophil cationic protein and other inflammatorymediators.In theurban atmosphere the respirable PM, which derives prevalently from car exhaustemissions, also plays a significant role in causing lung function impairement.It is usually a mixture of solid and liquid particles that vary in size,composition and origin. Penetration of PM into the tracheobronchial tract isrelated to its size and to the efficiency of the airways defence mechanisms. RespirablePM could induce adverse effects on airways not only acting directly, inducinginflammation of the mucous membranes, but also acting as a carrier of otherpollutants or allergens or by potentiating their effects. The latter effectcould contribute to explain the increase of cases of sensitization to pollenallergens in urban areas.