Love and allergies in the city beautiful—Chandigarh, India – Authors' reply
Authors: Dan L Crouse, Matilda van den Bosch, Paul J Villeneuve
Journal: The Lancet Planetary Health (2018)

We thank Kapil Goyal and Mini Singh for their interest in our recent Article1Crouse DL Pinault L Balram A et al.Urban greenness and mortality in Canada's largest cities: a national cohort study.Lancet Planet Health. 2017; 1: e289-e297Summary Full Text Full Text PDF PubMed Scopus (156) Google Scholar and Comment.2van den Bosch M Live long in nature and long live nature!.Lancet Planet Health. 2017; 1: e265-e266Summary Full Text Full Text PDF Scopus (7) Google Scholar While we agree generally that increases in urban greenery can lead to increases in pollens in the atmosphere, the evidence for a corresponding increase in allergy ailments is inconsistent.3Fuertes E Markevych I Bowatte G et al.Residential greenness is differentially associated with childhood allergic rhinitis and aeroallergen sensitization in seven birth cohorts.Allergy. 2016; 71: 1461-1471Crossref PubMed Scopus (90) Google Scholar Although we cannot comment on the situation in Chandigarh specifically, a Spanish cross-sectional study4Dadvand P Villanueva CM Font-Ribera L et al.Risks and benefits of green spaces for children: a cross-sectional study of associations with sedentary behavior, obesity, asthma, and allergy.Environ Health Perspect. 2014; 122: 1329-1335Crossref PubMed Scopus (211) Google Scholar of around 3000 children found no association between current asthma or allergic rhinoconjunctivitis and living near a forest, or with greenness measured within either 100 m, 250 m, 500 m, or 1000 m around the home. A recent cross-sectional study5Alcock I White M Cherrie M et al.Land cover and air pollution are associated with asthma hospitalisations.Environ Int. 2017; 109: 29-41Crossref PubMed Scopus (62) Google Scholar from England found that green space, gardens, and tree density were all associated with reduced hospitalisations for asthma, with varying levels of association depending on the corresponding levels of background air pollution. A large Canadian birth cohort6Sbihi H Tamburic L Koehoorn M Brauer M Greenness and incident childhood asthma: a 10-year follow-up in a population-based birth cohort.Am J Respir Crit Care Med. 2015; 192: 1131-1133Crossref PubMed Scopus (55) Google Scholar also reported decreased risk of developing asthma associated with residential surrounding greenness among preschool children (but no association among school-aged children). Elsewhere, another Canadian study7Sbihi H Koehoorn M Tamburic L Brauer M Asthma trajectories in a population-based birth cohort. Impacts of air pollution and greenness.Am J Respir Crit Care Med. 2017; 195: 607-613Crossref PubMed Scopus (59) Google Scholar reported that exposure to air pollution, but not greenness, was associated with increased risk of development of asthma. In our view, the existing evidence does not support the notion of a linear association between greenness and allergy ailments, suggesting that pollen levels alone do not explain any observed associations with allergic response, and that other environmental and sociodemographic characteristics, including medication use, might play an important role. As we described in our article, the benefits of increased urban trees and greenness have been associated in different contexts with reduced concentrations and exposures to air pollution, reduced exposures to noise and to extreme temperatures, ultraviolet protection, and increased opportunities for physical activity and social interactions. Thus, it is plausible that, in some cases, the protective effects of greenness could reduce pollen allergy response, in spite of increased exposure. Overall, we agree with the authors that strategic planting of specific kinds of trees and plants, in terms of species and genotype, is necessary for the purposes of maximising benefits to population health. We also acknowledge that when assessing the potential impacts of greenness on population health one needs to consider the complex interplay between the various environmental and social determinants of health pathways that could vary across a diverse series of adverse health outcomes. We declare no competing interests. Love and allergies in the city beautiful—Chandigarh, IndiaIn the past few decades, deforestation has undergone an enormous growth to meet the increasing demands of a growing population due to urbanisation. The boom in industry and vehicular congestion has degraded ambient air quality in most urban areas. All these factors have contributed to various health hazards as highlighted by Dan Crouse and colleagues.1 The authors showed the beneficial effects of increased urban greenness among urban Canadians, leading to a decrease in cause-specific mortality. In an accompanying Comment,1 Matilda van den Bosch2 highlighted that an inherent love for nature is a natural phenomenon and is useful in decreasing the stresses of urban life. Full-Text PDF Open AccessUrban greenness and mortality in Canada's largest cities: a national cohort studyIncreased amounts of residential greenness were associated with reduced risks of dying from several common causes of death among urban Canadians. We identified evidence of inequalities, both in terms of exposures to greenness and mortality risks, by personal socioeconomic status among individuals living in generally similar environments, and with reasonably similar access to health care and other social services. The findings support the development of policies related to creating greener and healthier cities. Full-Text PDF Open Access