Sources of Indoor Air Pollution and Respiratory Health in Preschool Children

Table 2

Studies analyzing the relationship between the use of gas in the home and the respiratory health in children under the age of five.

Location; Year; Author	Design	Sample population: Age; Number of cases	Disease studied		Exposure			Control variables	Results: adjusted OR/RR (IC 95%)
			Case definition	Information source	Source, chemical products	Evaluation	Exposure (%)
	Studies conducted in the United States
Tucson, USA; 1996; Aldous, et al. [8]	Cohorts	936 children followed by pediatricians during the first year of life	Lower respiratory tract illnesses (LRTIs); Three indicators: - First episode of LRTI of any kind (303); - First episode of LRTI with wheezing (196); - First episode of LRTI without wheezing (60)	Pediatric practice. Identified using clinical criteria, including imaging techniques (Rx)	Heating (gas, electric, steam, other); Cooker (electric, gas, oil, other)	Q administered by a nurse to the parents	Central gas heating (64%),; Gas heating through walls or floorboards (6%), other (30%); Cook range: Electric (61%); Gas (39%)	- Parents: educational level, ethnic group, history of hay fever or asthma; - Perceived lack of cleanliness in the neighborhood, no. of rooms, shared rooms; - Smoking; - Pets (dogs, cats); - No. of siblings and other children; - Child: sex, breastfeeding.	- OR LRTI gas heating (central or through walls/floorboards) versus other types of heating; - LRTI with wheezing; Central OR 1.2 (0.8–1.8); Walls/floorboards 1.6 (0.8–3.2); - LRTI without wheezing; Central OR 1.2 (068–2.2); Walls/floorboards 1.6 (0.3–3.9)
Connecticut and Virginia; 2002; Triche, et al. [9]	Cohorts	890 children followed for the first year of life	Episodes/Days of wheezing and episodes/days of cough during the winter months (October–April)	Interview and telephone call every 15 days	Gas heating	Q	2.8%	Sociodemographic factors; - Allergies and/or asthma in the mother; - Mother’s educational level; - Season of birth; - No. of children; - Breastfeeding	Gas heating: episodes with wheezing: 1.28 (0.99–1.67); Days with wheezing: 1.25 (1.05–1.50)
Connecticut and Massachusetts; 2003; Belanger et al. [10]	Cohorts	849 newborns with an asthmatic sibling; Followed for 1 year	Wheezing; Persistent cough; Days with symptoms during the first year of life: - None; - <30 d; - ≥30 d	Questionnaire mother/birth, 2–4, 6, 9, 12 months	Heating with gas, wood	Q	Gas: 34.2%; Wood: 5.9%	- Sex; - Ethnic group; - Parent with history of asthma; - Mother: allergies, smoking during pregnancy, educational level; - Family income; - Allergens (mites, cockroaches, cats, dogs); - Mold	OR; Wheezing; - Gas: 1.28 (0.88–1.86); - Wood: 0.76 (0.37–1.55); Persistent cough; - Gas: 1.52 (1.06–2.18); - Wood: 1.68 (0.89–2.30)
Connecticut and Massachusetts (USA); 2006; Belanger et al. [11]	Transversal	728 asthmatic children <12 years (<6 years: 66.5%) with an asthmatic sibling	Presence of and days with respiratory symptoms (wheezing, persistent cough, dysnea and intercostals muscle retraction) in the month prior to the Q	Questionnaire (mother)	Gas sources: heating, dryers	Q	Heating: 54.6%; Dryer: 7.4%	- Parent’s education and ethnicity; - Smoking, house characteristics, energy sources in the home; - Child’s age	Gas heating in multifamily houses: OR; Wheezing: 2.27 (1.15–4.47); Cough: 1.19 (0.66–2.16); Dysnea: 2.38 (1.12–5.06); Intercostal muscle retraction: 4.34 (1.756–10.69)
Studies conducted in Europe
Stockholm; (2002); Emenius et al. [12]	Case-control nested in the BAMSE cohort	Children between 0 and 2 years of age; Cases: 98; Controls: 195	Cases: persistent and/or recurrent wheezing; Controls: residents in the same area	Questionnaire at 2 months and at 1 and 2 years	Gas cooking ranges	Q	8.5%	- Sex; - Genetic history; - Mother’s age; - Smoking in the mother; - Breastfeeding; - Age of building	Use of gas cooking range; OR 1.72 (0.77–3.82)
Ashford (UK); Barcelona and Menorca; 2004; Sunyer et al. [13]	Cohorts	642 children (Ashford); 487 children; (Barcelona); 482 children; (Menorca); Followed for the first year of life	Incidence of Lower Respiratory Tract Infections (LRTIs) in the first year of life: Ashford 39.6%; Barcelona 28.4%; Menorca 45.3%; Use of antibiotics	Mothers’ comments, clinical histories, and history of antibiotic prescriptions; Monthly telephone call (Barcelona)	Gas cooking range, heating	Q	Gas cooking ranges: 60.12–74.13%; Gas heating: 24,69 a 83,49%	- Occupation of, allergies in, or atopy in parents; - Smoking; - Family size; - Outdoor NO2; - Breastfeeding	OR gas cooking range: 0.91 (0.69–1.20); OR gas heater: 1,01 (0,75–1,36)
Studies conducted in Africa and Asia
Zimbabwe; 2003; Mishra et al. [14]	Transversal	3559 children <5 years of age	Acute respiratory infection (ARI) (coughing with dysnea and tachypnea in the two weeks prior to the survey): 16% ARI	Children selected from a national health survey (Zimbabwe Demographic and Health Survey, ZDHS)	Cooking fuel: - Highly pollutant (wood, straw, dung); - Mildly pollutant (kerosene, coal); - Least pollutant (gas, electricity)	Q	66% of children live in homes in which highly pollutant cooking fuels are used	- Mother: age and educational level; - Socioeconomic level, residence (urban/rural), region, religion; - Child: age, sex, birth order, and nutritional state	OR (IC 95%) for ARI: - Least pollutant fuels (ref); - Mildly pollutant fuels: 1.33 (0.64–2.77); - Highly pollutant fuels: 2.20 (1.16–4.19)
Ludhiana, India.; 2002; Singh et al. [15]	Case-control	Cases: children between 1–15 years of age with persistent and/or recurrent cough (24); Controls: Randomly selected (500)	Persistent (>3 weeks) and/or recurrent (4 or more episode of over 10 days’ duration) cough in one year	Questionnaire (parents)	Smoke-producing fuels	Q (parents)		- Parents: socioeconomic level, history of illness.; - Smoking; - Type of house (pucca, kutcha, mixed).; - Hacinamient; - Pets	Use of smoke-producing fuel versus other type of fuel; OR (unadjusted): 1.49 (0.61–3.66); Adjusted correlation: t value = 1.668 (𝑃=.095)
Soweto, South Africa; 2006; Kristensen et al. [16]	Cohorts	Cohort of 571 children followed from birth throughout the first year of life.	Acute respiratory infection (ARI): 489 episodes; Incidence: 1.56 per child per year	Home visits by health care workers	Cooking fuel: electricity or gas versus paraffin/coal	Q; Inspection of homes	Electricity or gas (85%), paraffin/coal (15%)	- Parents: education, age; - Smoking; - Type of home; - Agglomeration of people; - Children: sex, birth weight, breastfeeding	RR (IC 95%) of ARI correlated to the use of electricity or gas versus paraffin or coal as a cooking fuel: All ARIs: 1.13 (0.84–1.52); Moderate/severe ARI: 0.65 (0.40–1.05)

LRTI: Lower respiratory tract infection; LRTI: lower respiratory tract infections; ARI: Acute respiratory infection; Q: questionnaire.