Protecting children's lungs by providing clean air during pregnancy?
Authors: Benoit Nemery, Patrick de Marie Katoto
Journal: The Lancet Planetary Health (2017)

Until a couple of decades ago, air pollution did not feature as a major determinant of ill health among infants. Thus, the words “air”, “pollution”, and even “smoking” are conspicuously absent from the WHO's 1978 Declaration of Alma-Ata, a major milestone in the field of public health, which expressed “the need for urgent action…to protect and promote the health of all the people of the world”.1International Conference on Primary Health CareDeclaration of Alma-Ata.WHO Chron. 1978; 32: 428-430PubMed Google Scholar Similarly, the United Nations (UN) Millennium Declaration of 2000 remained silent with regard to clean air.2General AssemblyResolution adopted by the General Assembly (A/res/55/2). United Nations Millenium Declaration.http://www.un.org/millennium/declaration/ares552e.htmDate: 2000Google Scholar Since then, things have changed and the medical community has become more aware that the health of children greatly depends on breathing clean air. Thus, the 2015 UN resolution that defined the agenda for sustainable development recognises the adverse health effects caused by air pollution, which should be “substantially reduced” by 2030.3General AssemblyResolution adopted by the General Assembly on 25 September 2015 (A/res/70/L.1). United Nations Sustainable Development Summit 2015. Sustainable Development Knowledge Platform.https://sustainabledevelopment.un.org/post2015/summitGoogle Scholar Air pollution now also features more prominently than before among the risk factors that determine the global burden of disease.4GBD 2015 Risk Factors CollaboratorsGlobal, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015.Lancet. 2016; 388: 1659-1724Summary Full Text Full Text PDF PubMed Scopus (2838) Google Scholar In particular, child mortality and morbidity in low-to-middle-income countries has been shown to be strongly associated with household air pollution caused by burning solid fuels (eg, coal, charcoal, wood, dung, and crop residues) for cooking and heating.5Gordon SB Bruce NG Grigg J et al.Respiratory risks from household air pollution in low and middle income countries.Lancet Respir Med. 2014; 2: 823-860Summary Full Text Full Text PDF PubMed Scopus (546) Google Scholar In The Lancet Planetary Health, Aneesa Vanker and colleagues7Vanker A Barnett W Workman L et al.Early-life exposure to indoor air pollution or tobacco smoke and lower respiratory tract illness and wheezing in African infants.Lancet Planet Health. 2017; 1: e238-e246Summary Full Text Full Text PDF Scopus (39) Google Scholar present findings from the Drakenstein Child Health Study,6Zar HJ Barnett W Myer L Stein D J Nicol MP Investigating the early-life determinants of illness in Africa: the Drakenstein Child Health Study.Thorax. 2015; 70: 592-594Crossref PubMed Scopus (113) Google Scholar a birth cohort study in two poor peri-urban communities, some 60 km outside of Cape Town, South Africa. More than 1100 pregnant women were enrolled in this study between 2012 and 2015 to investigate the early-life determinants of illness in an African population. Vanker and colleagues7Vanker A Barnett W Workman L et al.Early-life exposure to indoor air pollution or tobacco smoke and lower respiratory tract illness and wheezing in African infants.Lancet Planet Health. 2017; 1: e238-e246Summary Full Text Full Text PDF Scopus (39) Google Scholar focus on the effect of antenatal and postnatal exposure to indoor air pollution on the occurrence and severity of lower respiratory tract illness (LRTI) or wheezing in children followed up until 1 year of age. A major strength of this unique study,7Vanker A Barnett W Workman L et al.Early-life exposure to indoor air pollution or tobacco smoke and lower respiratory tract illness and wheezing in African infants.Lancet Planet Health. 2017; 1: e238-e246Summary Full Text Full Text PDF Scopus (39) Google Scholar besides its remarkably low loss to follow-up, is the unusually thorough assessment of individual exposure. This assessment included urinary cotinine measurements to estimate active and passive smoking, and more than 4500 antenatal and postnatal home visits, with 24-h air sampling for particulate matter of diameter 10 μm or less (PM10) and carbon monoxide, and 2 weeks' sampling of nitrogen dioxide, sulphur dioxide, and volatile organic compounds. In brief, the study mainly found increased risks of LRTI (incidence rate ratio 1·62, 95% CI 1·14–2·30; p=0·004) and of wheezing (2·09, 1·54–2·84; p<0·0001) if the mother smoked during pregnancy (depressingly, more than half of the mothers of mixed race smoked during pregnancy). High antenatal indoor exposure to fine dust—ie, PM10 levels above 40 μg/m3, the South African standard for ambient air—also increased risk of LRTI (1·43, 1·06–1·95; p=0·008) but not of wheezing. Postnatal exposures were generally less associated with risks of LRTI or wheezing. The possible effect of traffic-related pollution was not reported. In a subanalysis among children with LRTI, antenatal exposure to toluene above 240 μg/m3 was associated with significantly increased odds of hospitalisation (odds ratio 5·13, 95% CI 1·43–18·36; p=0·012) and requirement for oxygen (13·21, 1·96–89·16; p=0·008). An Australian case-control study8Rumchev K Spickett J Bulsara M Phillips M Stick S Association of domestic exposure to volatile organic compounds with asthma in young children.Thorax. 2004; 59: 746-751Crossref PubMed Scopus (342) Google Scholar found increased risks of asthma in young children with increasing toluene and benzene concentrations in the home, but it is unlikely that, at the observed concentrations, toluene (and similar volatile organic compounds, such as benzene) are causally implicated in the observed respiratory effects. Nevertheless, volatile organic compounds probably represent good markers of combustion-related pollution and they can be measured fairly easily and cheaply by diffusive samplers,9Awopeju OF Nemery B Afolabi OT et al.Biomass smoke exposure as an occupational risk: cross-sectional study of respiratory health of women working as street cooks in Nigeria.Occup Environ Med. 2017; 74: 737-744Crossref PubMed Scopus (9) Google Scholar as well as in urine.10Kicinski M Saenen ND Viaene MK et al.Urinary t, t-muconic acid as a proxy-biomarker of car exhaust and neurobehavioral performance in 15-year olds.Environ Res. 2016; 151: 521-527Crossref PubMed Scopus (10) Google Scholar Another promising approach to assess exposure to combustion-related pollution is to measure carbon particles in urine.11Saenen ND Bové H Steuwe C et al.Children's urinary environmental carbon load. A novel marker reflecting residential ambient air pollution exposure?.Am J Respir Crit Care Med. 2017; 196: 873-881Crossref PubMed Scopus (73) Google Scholar Our physical-chemical environment can be envisaged as a series of compartments that are imbricated like matryoshka dolls: the innermost doll is our internal milieu, the next compartment is the personal milieu (micro-environment), the next layers are the indoor environment (meso-environment) and the outdoor environment (macro-environment), and the final layer is the global or planetary environment. Obviously, all compartments communicate with each other. Hence, our internal milieu is polluted by substances absorbed from the external environment (and, sometimes, by chemicals released from prostheses, dental fillings, or tattoos). Importantly, during pregnancy the mother's internal milieu is also the external milieu of the fetus. Our personal micro-environment might be polluted by active smoking (so-called do-it-yourself air pollution), personal care products and cosmetics, and mobile phones, among other things. The meso-environment concerns the indoor spaces of homes, workplaces, and other buildings or vehicles, in which exposure to numerous types of pollutants can occur: cigarette smoke and other combustion products, substances released from building materials, household chemicals, and specific occupational agents. The outdoor environment is the one that people most often understand as the main environment to be affected by pollutants originating from industry, mining, power generation, agricultural activities, waste processing, urban traffic, among other things. In general, the concentrations of air pollutants are higher in indoor environments, especially if they are poorly ventilated, than in ambient urban air. Moreover, burning solid fuels or biomass causes not only indoor pollution, but also contributes substantially to ambient air pollution;12Chafe ZA Brauer M Klimont Z et al.Household cooking with solid fuels contributes to ambient PM2.5 pollution and the burden of disease.Environ Health Perspect. 2014; 122: 1314-1320Crossref PubMed Scopus (329) Google Scholar however, this has not been thoroughly quantified for Africa. Conversely, pollutants emitted by industry or traffic also penetrate into homes or schools, depending on building characteristics. Finally, at the planetary level, our environment is influenced by natural phenomena and by human activities that lead to transboundary transport of pollutants and climate changes. The Drakenstein Child Health Study is undoubtedly a landmark study and its findings are likely to be generalisable to other vulnerable populations, although even poorer and more polluted populations live in rural areas and mega-cities in sub-Saharan Africa. What are the study's implications, so far, in terms of the prevention of LRTI? Vanker and colleagues' rightly advocate effective measures to prevent smoking by women and limiting exposure to indoor air pollution, especially during the antenatal period.7Vanker A Barnett W Workman L et al.Early-life exposure to indoor air pollution or tobacco smoke and lower respiratory tract illness and wheezing in African infants.Lancet Planet Health. 2017; 1: e238-e246Summary Full Text Full Text PDF Scopus (39) Google Scholar Indeed, as shown in their other articles,13Zar HJ Bacterial and viral pneumonia. New insights from the Drakenstein Child Health Study.Paediatr Respir Rev. 2017; 24: 8-10Crossref PubMed Scopus (7) Google Scholar even excellent medical interventions directed at individuals, such as a high rates of antipneumococcal immunisation and successful prevention of mother-to-child HIV transmission, are unlikely to reduce substantially the incidence of childhood pneumonias in low-to-middle-income countries. Structural interventions leading to decreased poverty and improved air quality are likely to be more effective. Citizens worldwide are entitled to clean air, just like clean water.14Brunekreef B Annesi-Maesano I Ayres JG et al.Ten principles for clean air.Eur Respir J. 2012; 39: 525-528Crossref PubMed Scopus (40) Google Scholar We declare no competing interests. PdMK is recipient of a PhD bursary from the Marc Vervenne Fund. Early-life exposure to indoor air pollution or tobacco smoke and lower respiratory tract illness and wheezing in African infants: a longitudinal birth cohort studyAntenatal exposures were the predominant risk factors associated with LRTI or wheezing illness. Toluene was a novel exposure associated with severe LRTI. Urgent and effective interventions focusing on antenatal environmental factors are required, including smoking cessation programmes targeting women of childbearing age pre-conception and pregnant women. Full-Text PDF Open Access