Second-hand smoke (SHS) exposure is harmful to children and young people. They inhale double the amount of dust compared with adults, thus inhaling more smoke containing dust particles. They also have faster respiratory rates and narrower airways, meaning their SHS exposure is higher. SHS causes an increased incidence of respiratory infection, cough, increased sputum load, preschool wheeze, and asthma, and is also associated with significantly decreased lung function. It worsens pre-existing chronic respiratory conditions, including being a trigger for asthma attacks and contributing to the pathogenesis of asthma and pre-school wheeze. Additional medications and unscheduled hospital visits may indeed be required if asthma becomes more severe due to SHS, and it can contribute to steroid insensitivity in severe asthma and cause airway neutrophilia.A new threat has been discovered—third-hand smoke (THS) exposure. This is when the toxins or persistent residue produced from SHS or environmental tobacco smoke (ETS) accumulate in dust and on surfaces in homes where tobacco has been used and is re-emitted into air. THS becomes increasingly more toxic with time, which is a problem for children in exposed homes. Mouse models of THS exposure showed harm to multiple organs and high concentrations of inflammatory cytokines in the lung.

During the past year, COVID-19 has necessitated numerous lockdowns, including the closure of schools, causing children and young people to spend more time in their homes. For some children, whose family members smoke, more time at home has meant increased SHS and THS exposure, whereas the school and after-school environment are smoke-free. In addition, parents or other family members might be home working, and so where they would usually smoke away from their home, for example when they go to their workplace, they are now smoking at home.

The impact on children from lower socioeconomic classes is likely greater than those from higher socioeconomic backgrounds, as they are more likely to be exposed to ETS and to live in smaller living environments with less access to outdoor space. In addition, one study (which excluded children who had a smoker inside their home) found that children living in flats had 45% higher cotinine levels than those in detached houses, as smoke seeps through walls and shared ventilation systems.

We aimed to ascertain the changing habits of smoking or ex-smoking parents of children and young people with severe respiratory disease, identified from a tertiary paediatric respiratory clinic during the pandemic. We gave 50 parents an 11-point questionnaire (panel) to respond to over the telephone (January–February, 2021). These parents had been previously identified as they had engaged in our smoking cessation clinic. During this questionnaire, we asked about changing smoking habits and asked about how hard they had found the pandemic, giving an idea of stress levels during lockdown.Panel11-point questionnaire given to parents•

How many children do you have and how old are they?

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Do you smoke?

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Did you smoke prior to lockdown?

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How many cigarettes per day?

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Does your child have a condition whereby their doctors advised to shield?

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Have you a house or a flat or maisonette?

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Do you have access to outside space?

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Do others in your house smoke?

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Have you used methods to give up smoking in the past?

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Have you been working from home?

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On a scale of 1–10, how hard have you found the lockdown?

41 (82%) children whose parents were called had asthma, 6 (12%) had cystic fibrosis, and all the other patients had other respiratory conditions. Briefly, two thirds of parents who smoked before the pandemic were smoking the same amount or more during lockdown (figure). This caused a substantial proportion of children and young people with respiratory conditions to be exposed to an increased amount of harmful ETS as they spent more time at home. A considerable number of children (mean 2·5 [range 1–8]) in a household were exposed to parental ETS. In 13 (29%) of 49 smoking households, more than one family member smoked, and in three (6%) of 49 smoking households, the child with a respiratory condition was required to shield during lockdown—both of which would have increased the child's exposure to SHS and THS.

FigureChanges in smoking behaviour of parents (n=50) (A) and scores of hardship (B) during the pandemic

17 (34%) of parents were vaping in addition to smoking during lockdown. E-cigarettes can produce toxic substances and leave deposits of nicotine on surfaces when used inside.Smokers scored highly on how hard they found the lockdown and most said this was due to stress (figure). For some, this increased stress caused them to smoke more. The stress encountered by the parents might also have been absorbed by the children themselves.Although this study has revealed that the pandemic has resulted in an increase in passive smoke exposure to vulnerable children and young people, adverse outcomes, such as asthma attacks and hospitalisations during the pandemic, were not widely reported. This observation might have been due to improved compliance with medication, reluctance to use health-care facilities at times of peak COVID-19 admissions, and less exposure to other triggers, such as viral infections picked up at school and pollen. Outdoor air pollution was reduced during lockdown, which could also have had an effect.

Although, children and young people continue to be mostly, but not completely, spared the worst health outcomes of the pandemic, the collateral effects appear to have had substantial detrimental effects. Knowledge of increased passive smoke exposure by SHS and THS will allow for more targeted history taking in high-risk patients and referral to smoking cessation clinics if appropriate. If future lockdowns occur, it is necessary to prioritise high-risk patients and provide virtual smoking cessation advice promptly, to limit both SHS and THS exposure. We did not have resources for virtual smoking cessation programmes in lockdown, but this should be prioritised in future.

Increased education on the harmful effects of both SHS and THS should be given to families in the community to try to influence parental habits, and adults need to understand the harmful effects of ETS and e-cigarettes to help improve the health of their children.

We declare no competing interests.

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DOI: https://doi.org/10.1016/S2213-2600(21)00231-9

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