"Babies and young children in prams can be exposed to up to 60% more pollution than adults, a study suggests," BBC News reports.
The headline is prompted by a review of previously conducted studies on air pollution and possible adverse effects on young children. One study found that pollution from a diesel lorry was 59% higher at pram height compared to adult height. But there were also findings from other studies which found levels were higher for adults.
The research suggests that putting covers over prams may be beneficial, but did not test this hypothesis. There is also the possibility that covering prams may trap in pollutants making the situation worse.
The health risks of air pollution depend on how often you are exposed, and for what length of time. While this research can't provide conclusive evidence about babies being exposed to more pollution than adults, it does support current efforts in the UK to reduce particulate air pollution.
Where did the story come from?
The study was carried out by researchers from the Global Centre for Clean Air Research at the University of Surrey and was funded by the University of Surrey and the Engineering and Physical Sciences Research Council. The study was published in the peer reviewed journal Environment International.
There was fairly wide and variable coverage, in terms of quality and accuracy, from the UK media. The Sun inaccurately claimed that the researchers had "tested the inside of 160 prams", while the Mail Online said they had "analysed more than 160 studies investigating air pollution". However, the researchers did neither of these things; they performed a review of the literature and included 5 studies that measured air pollution levels. Only 2 of these studies actually had pollution monitors inside a pram.
What kind of research was this?
This study is a review of already published scientific and grey literature (evidence not published on a commercial or academic basis, such as government research) on in-pram babies and their exposure to traffic generated air pollutants.
A review of the literature aims to provide an overview of some, but not all of the literature on a topic. This means some articles may have been missed, or the authors could have picked out research that was particularly useful to their research question, which leads to bias in the reporting of the included studies. A simple review of the evidence is not as comprehensive as a systematic review, where efforts are made to find all the relevant literature on the topic in question.
What did the research involve?
The researchers included literature which assessed:
- how much pollution children in prams could be exposed to compared to adults
- the types of chemicals in the pollution
- possible solutions to prevent babies being exposed to in-pram pollution (researchers included pushchairs, buggies, strollers and 3-wheelers in their definition of prams)
The researchers only included literature that assessed outdoor pollution, and excluded literature assessing exposure to pollution in indoor environments such as schools and homes where a number of review articles were already available.
What were the basic results?
Only 5 studies assessed pollutant concentrations at different heights and the findings were mixed:
- in 1 study, pollutants in prams were 5% lower than adults in the morning and 10% higher in the afternoon
- 2 studies measuring pollutants at different heights found pollutant concentrations were 5 to 15% higher up to a level of 0.8 meters compared to adult height
- the pollutants level was 59% higher at the height of a pram compared to an adult in 1 study; researchers used a mannequin taking in air at different heights next to a road while a diesel truck drove back and forwards
- a further study, not included in the results table, found levels were 17-51% higher for adults than children in buggies
Other results were as follows:
- the average breathing height of prams was between 0.55 and 0.85m (2ft)
- the weather, such as wind speed, and the amount of traffic on the roads is likely to affect the amount of pollution
- the chemicals in the pollution includes toxic metals which have previously been linked to damaging the frontal lobe of the brain, and affecting cognition and brain development
- protective covers for prams and other technological solutions were suggested but there are no definitive results to show how effective these can be
How did the researchers interpret the results?
The researchers conclude that "air pollution exposure to in-pram babies poses a serious threat to their early childhood development, necessitating a need for effective mitigation measures". They say that "technological solutions such as creating a clean air zone around the breathing area can provide instant solutions". They go on to state that "future research is also needed to understand the impact of community empowerment and public policy instruments in mitigating young children's exposure to air pollution".
This review does not present enough evidence to say definitively that babies are exposed to more pollution than the person pushing the pram. The widely reported figure of 60% higher levels of pollution came from a single US study. The other studies found in this review had mixed results, with some indicating higher levels at adult height compared to pram height.
The review was also neither able to say if the style or type of pram made any difference to exposure to pollutants, nor whether using a cover would be better or actually trap in any pollutants.
Despite the limitations of this study, there is evidence outlining the effects of pollution and its negative effects on the development of diseases such as coronary heart disease, stroke, lung cancer and childhood asthma, therefore tackling air pollution is already a government priority. This research does not have the methodological strength to add anything new to current research in the area however.
There are things people can do to avoid their overall exposure to air pollution, such as avoid going outside in peak traffic times, reducing the time spent near busy roads, and checking local air pollution levels on websites such as Defra's UK Air Information Resource.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
BBC News, 14 August 2018
The Sun, 14 August 2018
The Daily Telegraph, 14 August 2018
Mail Online, 14 August 2018
The Times (subscription required), 14 August 2018
Links to the science
Environment International. Published online August 10 2018