Clinical Scenario 6 for Particle Pollution
Mrs. K. is a 35-year-old non-smoker who comes to your office because of seasonal allergy symptoms (rhinitis, conjunctivitis) that she cannot sufficiently control with the over-the-counter medication she has used in the past. She denies wheezing or chest tightness. Apart from her mild allergy to pollen, which has manifested during springtime over several years, her past medical history is not significant.
A thorough environmental history reveals that she lives in a neighborhood that was once rural, but has grown substantially over the last couple of years and has become a high-density residential area. She likes to jog around the neighborhood every afternoon when she returns from her work as a secretary in an insurance office. Nobody in her household smokes and she does not have any pets. She is not allergic to any food. After excluding all major risks factors, you decide that it is unnecessary to do any allergy or pulmonary function tests at this time. However, when you are taking her environmental history, she mentions that traffic in the neighborhood where she runs after work is much heavier than it used to be.
In residential areas, the traffic-generated particle pollution comes primarily from the exhaust of gasoline engines and crustal particles (road abrasion, soil dust, and tire wear), resuspended particles including pollen, and particles transported from other areas. The relative contribution from these sources to the total pollution level varies with meteorological conditions, seasons, and traffic density. This airborne particle pollution comprises coarse as well as fine fractions.
Several studies report that exposure to traffic-generated pollutants may cause bronchial hyper-responsiveness, increase sensitization to common allergens, and induce allergic inflammation of the airways and respiratory symptoms in more sensitive individuals (Wyler et al., 2000). It is postulated that particle pollution, as well as carrying attached allergens, may enhance the allergic potential of the attached allergen. A study of close to 7,000 children reported that living in an area with moderately increased air pollution over the years is associated with increased atopy and prevalence of respiratory symptoms (Penard-Morand et al., 2005). However, despite the numerous studies reporting a strong association between traffic-generated pollution and allergic sensitization in children, studies of adult populations are inconsistent, and the aggravating effects of air pollution on the severity of allergies are still open for discussion.
Excluding other potential factors (such as increased indoor allergen levels at home or work) that may have contributed to the worsening of Mrs. K.’s symptoms, you may consider traffic pollution as a potential aggravating factor. Increased pollen count in the ambient air due to traffic, as well as adjuvant effect of suspended particle pollution and gaseous pollutants, are likely factors leading to her more frequent and severe allergies. Changing the venue for her afternoon running (e.g., to a park), or switching to early mornings before local traffic picks up, may reduce the frequency and severity of her allergies. If so, it will suggest that the environmental exposure is a significant contributor to her increased allergy symptoms.