Can individual protective measures safeguard cardiopulmonary health from air pollution? A systematic review and meta-analysis

Evidence supporting the effect of individual protective measures (IPMs) on air pollution is relatively scarce. In this study, we performed a systematic review and meta-analysis to investigate the effects of air purifiers, air-purifying respirators, and cookstove changes on cardiopulmonary health outcomes. We searched PubMed, Scopus, and Web of Science until December 31, 2022, 90 articles and 39,760 participants were included. Two authors independently searched and selected the studies, extracted information, and assessed each study's quality and risk of bias. We performed meta-analyses when three or more studies were available for each IPMs, with comparable intervention and health outcome. Systematic review showed that IPMs were beneficial in children and elderly with asthma along with healthy individuals. Meta-analysis results showed a reduction in cardiopulmonary inflammation using air purifiers than in control groups (with sham/no filter) with a decrease in interleukin 6 by -0.247 μg/mL (95% confidence intervals [CI] = -0.413, -0.082). A sub-group analysis for air purifier as an IPMs in developing counties reduced fractional exhaled nitric oxide by -0.208 ppb (95% confidence intervals [CI] = -0.394, -0.022). However, evidence describing the effects of air purifying respirator and cook stove changes on cardiopulmonary outcomes remained insufficient. Therefore, air purifiers can serve as efficient IPMs against air pollution. The beneficial effect of air purifiers is likely to have a greater effect in developing countries than in developed countries.

The Effects of Household Air Pollution (HAP) on Lung Function in Children: A Systematic Review

The World Health Organization (WHO) estimates that around 3 billion people today are exposed to smoke from the household combustion of solid fuels. While the household use of solid fuels has decreased over the last few decades, it remains a leading modifiable risk factor for the global burden of disease. This systematic review analyzed the impact of Household Air Pollution (HAP) on lung function in children (under 18 years of age), as this is the time period of accelerated growth rate until full skeletal maturity. Data from 11 published studies demonstrated that exposure to smoke from solid fuel was associated with a lower growth rate of several lung function indices (FVC, FEV₁, FEF_25–75) in children. However, there was no observed association between HAP and the FEV₁/FVC ratio over time. Although the evidence suggests an inverse association between high exposure to HAP and lung function indices, there is a lack of longitudinal data describing this association. Therefore, precaution is needed to reduce the smoke exposure from solid fuel burning.

Household solid fuel use and peak expiratory flow in middle-aged and older adults in China: A large cohort study (2011-2015)

Indoor air pollution caused by solid fuel use in cooking and heating in China is common. The relationship between household solid fuel use and peak expiratory flow (PEF) in middle-aged and older adults in China has not been clarified. The aim of this study was to assess the relationship between long-term household solid fuel use (clean for both cooking and heating, solid for either cooking or heating, and solid for both cooking and heating) and PEF changes in middle-aged and older adults using a nationally representative prospective cohort. Covariance analysis was used to compare PEF changes in different indoor air pollution exposure groups. Separate analysis of cooking and heating as well as sub-group analyses by age, sex and smoking status were conducted, linear mixed growth model analysis was used to evaluate the association between cooking fuel type and PEF. A total of 6818 participants were enrolled in the cohort analysis. Results revealed that solid fuel use in cooking and heating separately or conjointly were associated with reduced PEF (solid fuel use in cooking: least square mean [LSM] = 19.9, 95% confidence interval [CI]: 11.5-28.2, P = 0.03; solid fuel use in heating: LSM = 19.4, 95% CI:11.2-27.5, P = 0.04; both solid fuel use: LSM = 17.6, 95% CI: 9.3-25.9, P for trend <0.0001), especially in participants aged >65 years (LSM = -9.22, 95% CI: 27.9-69.52, P for trend <0.0001), females (LSM = -6.41, 95% CI: 19.12-6.30, P for trend <0.0001) and current or former smokers (LSM = -21.55, 95% CI: 36.14 to -6.97, P < 0.02). Compared to that of participants using clean fuels for cooking, PEF of participants using solid fuels were decreased by 3.5 l/min per 2 years over a 4-year follow-up. This cohort study highlights the adverse effects of indoor air pollution on lung function in middle aged and older adults in China.

Positive impact of improved cookstove usage on respiratory health in Congolese refugees: a prospective cohort study

Around 3 billion people worldwide use solid biomass fuels for cooking. Exposure to indoor biomass smoke is an important cause of COPD and therefore a target of many public health interventions, such as usage of improved cookstoves. The aim of our study was to show whether usage of improved cookstoves can lead to relevant improvement in lung function and CAT-score in a well characterized population including a subgroup of this population with preexisting airway obstruction. Interviews and spirometry were performed in Congolese women living in an UNHCR (United Nations High Commissioner for Refugees) refugee camp in Rwanda before (baseline, BL) and 9 months after (follow-up, F9) they received an energy-efficient cookstove (Save80) and were trained how to use it. Two hundred sixty-two women completed both spirometry and interview appropriately at BL and F9 and were included in per protocol (pp) analysis, which showed no change in mean FEV1. The predefined subgroup of this population with airway obstruction at baseline (N = 31) showed a significant FEV1 increase (FEV1_F9 = 1.70 L; p < 0.01 vs FEV1_BL = 1.58 L, p < 0.01). Median CAT-scores were significantly lower in the F9 assessment. Our data indicate that usage of improved cookstoves has a positive impact on respiratory health especially in individuals with preexisting airway obstruction. Further studies to investigate long-term outcome are warranted.

Association between choice of cooking fuel and peak expiratory flow rate among rural women in the Niger Delta, Nigeria

Background: Long-term exposure to indoor air pollution from biomass fuel combustion is a risk factor for respiratory disease, which is an increasingly prevalent contributor to morbidity and mortality in low- and middle-income countries. This study evaluated the association between household fuel use and the peak expiratory flow rate (PEFR) of rural-dwelling women in selected communities of the Niger Delta. Methods: This was a cross-sectional study including 321 non-smoking women aged 18 years and older. Questionnaires were used to obtain data on predominant fuel used and a brief medical history. Women with current respiratory symptoms were excluded. Fuel use was classified into three categories: biomass fuels (BMF), such as wood, animal dung and coal, kerosene and liquefied petroleum gas (LPG). The PEFR was measured with an Omron peak flow meter using standard protocols and was abnormal if it was less than 80% of predicted value based on age and height. Results: The mean age of the 321 women was 38.5±14.2 years. The biomass fuel users had significantly lower PEFR (353.9±104.4) compared to kerosene users (376.2±70.1) and LPG users (393.6± 93.3) (p=0.030). The overall prevalence of abnormal PEFR was 22.4%. The PEFR was abnormal in more BMF users (28%) than kerosene users (13.4%) and LPG users (9.4%) (p=0.005). The PEFR of women who used LPG was 20.8 l/min higher than BMF users (p=0.012). The users of BMF were 5.8 times more likely to have abnormal PEFR than LPG users (OR 5.8, 95% CI 1.62, 20.52, p=0.007). Conclusion: In this population, the use of biomass fuel was significantly associated with abnormal PEFR. This needs to be further explored in this population with a larger study using more objective measures, such as spirometry testing, to guide policies for the implementation of preventive strategies to protect vulnerable women from chronic obstructive airway disease.

Impact of improved cookstoves on women's and child health in low and middle income countries: a systematic review and meta-analysis

OBJECTIVES

Improved biomass cookstoves may help reduce the substantial global burden of morbidity and mortality due to household air pollution (HAP) that disproportionately affects women and children in low and middle income countries (LMICs).

DESIGN

Systematic review and meta-analysis of (quasi-)experimental studies identified from 13 electronic databases (last update: 6 April 2018), reference and citation searches and via expert consultation.

SETTING

LMICs PARTICIPANTS: Women and children INTERVENTIONS: Improved biomass cookstoves MAIN OUTCOME MEASURES: Low birth weight (LBW), preterm birth, perinatal mortality, paediatric acute respiratory infections (ARIs) and COPD among women.

RESULTS

We identified 53 eligible studies, including 24 that met prespecified design criteria. Improved cookstoves had no demonstrable impact on paediatric lower ARIs (three studies; 11 560 children; incidence rate ratio (IRR)=1.02 (95% CI 0.84 to 1.24)), severe pneumonia (two studies; 11 061 children; IRR=0.88 (95% CI 0.39 to 2.01)), LBW (one study; 174 babies; OR=0.74 (95% CI 0.33 to 1.66)) or miscarriages, stillbirths and infant mortality (one study; 1176 babies; risk ratio (RR) change=15% (95% CI -13 to 43)). No (quasi-)experimental studies assessed preterm birth or COPD. In observational studies, improved cookstoves were associated with a significant reduction in COPD among women: two studies, 9757 participants; RR=0.74 (95% CI 0.61 to 0.90). Reductions in cough (four studies, 1779 participants; RR=0.72 (95% CI 0.60 to 0.87)), phlegm (four studies, 1779 participants; RR=0.65 (95% CI 0.52 to 0.80)), wheezing/breathing difficulty (four studies; 1779 participants; RR=0.41 (95% CI 0.29 to 0.59)) and conjunctivitis (three studies, 892 participants; RR=0.58 (95% CI 0.43 to 0.78)) were observed among women.

CONCLUSION

Improved cookstoves provide respiratory and ocular symptom reduction and may reduce COPD risk among women, but had no demonstrable child health impact.

REGISTRATION

PROSPERO: CRD42016033075.