[Allergic respiratory diseases and outdoor air pollution]

A review on the role of dispersion and receptor models in asthma research

There is substantial evidence that air pollution exposure is associated with asthma prevalence that affects millions of people worldwide. Air pollutant exposure can be determined using dispersion models and refined with receptor models. Dispersion models offer the advantage of giving spatially distributed outdoor pollutants concentration while the receptor models offer the source apportionment of specific chemical species. However, the use of dispersion and/or receptor models in asthma research requires a multidisciplinary approach, involving experts on air quality and respiratory diseases. Here, we provide a literature review on the role of dispersion and receptor models in air pollution and asthma research, their limitations, gaps and the way forward. We found that the methodologies used to incorporate atmospheric dispersion and receptor models in human health studies may vary considerably, and several of the studies overlook features such as indoor air pollution, model validation and subject pathway between indoor spaces. Studies also show contrasting results of relative risk or odds ratio for a health outcome, even using similar methodologies. Dispersion models are mostly used to estimate air pollution levels outside the subject's home, school or workplace; however, very few studies addressed the subject's routines or indoor/outdoor relationships. Conversely, receptor models are employed in regions where asthma incidence/prevalence is high or where a dispersion model has been previously used for this assessment. Road traffic (vehicle exhaust) and NOx are found to be the most targeted source and pollutant, respectively. Other key findings were the absence of a standard indicator, shortage of studies addressing VOC and UFP, and the shift toward chemical speciation of exposure.

[Mite sensitization in children followed for respiratory allergy in a tropical African environment in Cotonou, Benin]

INTRODUCTION

In tropical Africa, allergies are not well documented. The objective of this work was to evaluate, by two methods, the sensitization to mites in children followed for respiratory allergy.

METHODS

Skin prick-test and IgE assay by REAST test with 3 mites: Dermatophagoides pteronyssinus (D. pteronyssinus), Dermatophagoides farinae (D. farinae) and Blomia tropicalis (B. tropicalis) were carried out in children from 3 to 15 years followed up for asthma and/or allergic rhinitis. The positive results of the two tests were compared.

RESULTS

Of the 130 (100%) children included, all eligible for the assay, 119 (91.5%) had the prick-test. The mean age and sex ratio (M/F) were 7±1 year, and 1.6. The association of rhinitis and asthma was the most frequent and found in 66 (55.6%). The sensitivity frequencies for the prick-test and assay were respectively 79% versus 36.1% for B. tropicalis, 71.4% versus 33.4% for D. pteronyssinus and 38.7% versus 37.8% for D. farinae. A moderate correlation between mean papule diameter and mean IgE concentration was observed.

CONCLUSION

In African tropical environments, dust mite sensitization in children followed for respiratory allergy is frequent, with the order of frequency being: B. tropicalis, D. pteronyssinus, and D. farinae. The prick-test had better sensitivity than the assay for its evaluation.

[Health effects of diesel exhaust: a state of the art]

INTRODUCTION

This review presents the state of knowledge regarding the acute and chronic toxicity of diesel engine exhaust in humans.

STATE OF ART

The health effects of diesel engine exhaust, which is a complex mixture of gas and particulate matter (ultrafine and fine particles), are mainly irritation of the respiratory tract and carcinogenicity. They may also facilitate the development of respiratory allergies. A recent reassessment by the International Agency for Research on Cancer concluded that there is sufficient evidence of a causal association between exposure to diesel engine exhaust and lung cancer.

PERSPECTIVES

The epidemiologic data collected during the last two decades also show limited evidence of increased risks of bladder cancer, as well as of chronic obstructive pulmonary disease in diesel engine exhaust exposed workers. Both experimental and epidemiological studies have involved the effect of emissions from traditional diesel engine technology. Major developments in this technology have occurred recently and the toxicity of emissions from these new engines is still to be characterized.

CONCLUSION

Further studies are needed to explore the link between diesel engine exhaust exposure and the risks of bladder cancer, as well as of chronic obstructive pulmonary disease and respiratory allergies. Research is also needed to get more information about the toxicity of the new diesel technology emissions.

Poor air quality in classrooms related to asthma and rhinitis in primary schoolchildren of the French 6 Cities Study

Background

Relationships between indoor air quality (IAQ) found in schools and the allergic and respiratory health of schoolchildren have been insufficiently explored. A survey was conducted in a large sample of classrooms of primary schools in France to provide objective assessments of IAQ to which young schoolchildren are exposed in classrooms, and to relate exposure to major air pollutants found in classrooms to asthma and allergies of schoolchildren.

Methods

Concentrations of fine particles with aerodynamic diameter ≤2.5 μm (PM_2.5), nitrogen dioxide (NO₂) and three aldehydes were objectively assessed in 401 randomly chosen classrooms in 108 primary schools attended by 6590 children (mean age 10.4 years, SD ±0.7) in the French 6 Cities Study. The survey incorporated a medical visit including skin prick testing (SPT) for common allergens, a test for screening exercise-induced asthma (EIA) and a standardised health questionnaire completed by parents.

Results

Children were differently exposed to poor air quality in classrooms, with almost 30% being highly exposed according to available standards. After adjusting for confounders, past year rhinoconjunctivitis was significantly associated with high levels of formaldehyde in classrooms (OR 1.19; 95% CI 1.04 to 1.36). Additionally, an increased prevalence of past year asthma was found in the classrooms with high levels of PM_2.5 (OR 1.21; 95% CI 1.05 to 1.39), acrolein (OR 1.22; 95% CI 1.09 to 1.38) and NO₂ (OR 1.16; 95% CI 0.95 to 1.41) compared with others. The relationship was observed mostly for allergic asthma as defined using SPT. A significant positive correlation was found between EIA and the levels of PM_2.5 and acrolein in the same week.

Conclusions

In this random sample, air quality in classrooms was poor, varied significantly among schools and cities, and was related to an increased prevalence of clinical manifestations of asthma and rhinitis in schoolchildren. Children with a background of allergies seemed at increased risk.