Table 1.
Magnitude of effect of environmental exposure on respiratory symptoms
| Exposure | Magnitude of effect (95% CI) |
|---|---|
| SHS | |
| Antenatal exposure | 1.7 (1.2 to 2.3)‡12 1.13 (1.04 to 1.23)*13 2.1 (1.2 to 3.7)†14 1.35 (1.13 to 1.62)†15 4.0 (1.9 to 8.6)*16 No association17 |
| Postnatal exposure | 1.3 (1.1 to 1.6)†‡5 1.2 (1.0 to 1.3)*18 2.9 (1.1 to 7.2)*17 1.7 (1.1 to 2.58)†19 4.2 (1.4, 13.0) for exposure to high fine particulate*20 |
| Domestic combustion | |
| Gas cooking | No association21 |
| Fine particulates (PM2.5) | 1.5 (1.1 to 2.2) per quartile PM2.5 increase*22 |
| Detectable Sulfur Dioxide | OR 1.8 (1.1 to 3.1)*23 |
| Incense | No association24 1723 |
| Biomass | 4.3 (3.0 to 5.0)†25 |
| Inhaled chemicals | |
| VOC | 1.2 (1.01 to 1.4) per 10 µg/m3 increase†26 4.2 (1.4 to 12.9)¶27 2.1 (1.1 to 3.9) per µg/m3 of total MVOC*28 1.39 (no CI given)†29 2.92 (2.25 to 3.75)†30 |
| Chlorinated swimming pools | 0.5 (0.3 to 0.9)†31 No association ¥32 |
| Other chemicals | 1.7 (1.2 to 2.4)*34 (cleaning agents) |
| 1.6 (1.2 to 2.1)†‡33 (PVC) | |
| 1.9 (1.1 to 3.2)†35 (pyrene) | |
| 0.7 (0.5 to 0.9)*36 (maternal BPA) | |
| 1.4 (1.0 to 1.9)*36 (child BPA) | |
| 2.8 (2.0 to 3.9)†37 and 1.7 (1.01 to 2.9)*38 (oil refinery) | |
| Damp housing/mould | 1.5 (1.3 to 1.7)†‡39 1.4 (1.1 to 1.8))*‡40 (no association at 6–8 years) 7.1 (2.2 to 12.6)†41 2.4 (1.1 to 5.6)†42 for exposure 2.6 (1.1 to 6.3)43 per unit increase in mould index 1.8 (1.5 to 22)44 per unit increase in mould index |
| Multiple exposures | 0.7 (0.5 to 0.9)‡48 0.4 (0.3 to 0.8)‡49 3.0 (1.1 to 7.9) for high HDM† and 1.2 (1.1 to 1.4)* per quartile LPS increase50 1.8 (1.02 to 3.0)* increasing cockroach allergen55 and 0.3 (0.1 to 0.98)* for dog and 0.6 (0.4 to 1.01)* for cat exposure55 2.6 (1.3 to 5.4)† for high cat exposure51 2.7 (1.1 to 7.1)† dog and SHS to 4.8 (1.1 to 21.5)† dog and elevated NO256 3.1 (1.8, 5.2)* for exposure to SHS, infection and no breast feeding57 |
| No association‡45‡ 46‡ 47 52–54 | |
| Inhaled allergens/particles | |
| Pet | 0.7 (0.6 to 0.9)†‡ cat exposure59 1.1 (1.0 to 1.3)†‡ dog exposure59 4.7 (1.2 to 18.0)† cat exposure61 0.6 (0.4 to 0.9)* cat exposure62 0.3 (0.1 to 0.81)* cat exposure63 1.2 (1.1 to 1.3)* cat exposure64 No association‡60 65 66 |
| Other exposures | 1.5 (1.1 to 2.1)* highest vs lowest quartile LPS exposure68 1.4 (1.1 to 1.7)* mouse allergen69 0.4 (0.2 to 0.6)† feather quilt70 1.8 (1.0 to 3.2)† number of synthetic bedding items71 No association cockroach52 |
| HDM | No association‡72‡73 74 |
| Outdoor allergens | OR 3.1 (1.3 to 7.4)* birthday during fungal spore season75 OR 1.4 (1.1 to 1.7)† grass pollen exposure76 RR 1.2 (1.02 to 1.3)† tree canopy cover77 |
| Air pollution | 1.05 (1.00 to 1.11)†‡ per ppm increased NO278 1.02 (1.00 to 1.04)†‡ per ppm increased NO78 1.06 (1.01 to 1.12)†‡ per ppm increased CO78 1.04 (1.01 to 1.07)*‡ per ppm increased SO278 1.05 (1.04 to 1.07)*‡ per unit increase particulates78 1.04 (1.01 to 1.07)* per ppm increased CO79 1.2 (1.0 to 1.31)† per 5ppb increase NO280 2.0 (1.2 to 3.6)† traffic-related particles82 1.3 (1.0 to 1.6)† higher traffic density84 3.1 (1.3 to 7.4)† high exposure to PM2.585 No association81 |
| Dietary exposures | |
| Maternal dietary components during pregnancy | 0.2 (0.08 to 0.6)†‡ Mediterranean diet86 0.6 (0.4 to 1.0)* Western diet88 0.6, (0.3 to 0.96)* fish consumption89 0.8 (0.7 to 1.0) peanuts and 0.8 (0.7 to 0.8) tree nuts†90 1.6 (1.2 to 2.0) low vegetables 1.5 (1.2 to 1.8) low fruit and chocolate 1.4 (1.1 to 1.7)†91 No association fish oil87‡, butter and margarine92 |
| Specific nutrient intake during pregnancy | 0.6 (0.4 to 0.7)*‡ increased vitamin D intake86 0.7 (0.5 to 0.9)*‡ increased vitamin E intake86 0.3 (0.1 to 0.4)*‡ increased plasma vitamin A86 0.95 (0.91 to 0.99)* per 10 nmol/L increase cord vitamin D97 No association vitamin D (plasma)93–95 (intake)96, dietary antioxidants99 or folate100 or vitamin A101 supplements |
| Breast feeding | OR 0.92 (0.86 to 0.98)*‡102 OR 1.1 (1.0 to 1.2)†‡102 1.4 (1.2 to 1.7)* never breast feeding103 0.9 (0.8 to 0.96)† exclusive breast feeding104 2.0 (1.0 to 3.8)† maternal margarine intake during lactation98 No association‡105 |
| Cow’s milk formula | RR 0.4, (0.2 to 0.9)*‡ hydrolysed vs standard106 OR 0.3 (0.1 to 1.0)* fatty acid supplementation108 No association109 |
| Infant diet | 0.4 (0.2 to 0.9) for youngest vs oldest age at introduction of wheat†111 0.6 (0.4 to 0.9) for early vs delayed introduction of fish115 No association with age at introduction of solids112 113 prebiotic supplementation‡117 ‡118 or vitamin supplementation119 |
| Child diet | 0.6 (0.4 to 0.9)† full cream milk121 1.5 (1.04 to 2.1) Western diet124 0.93 (0.85 to 1.00) per fruit item consumption/day/week125 0.5 (0.3 to 0.6) for highest vs lowest tertile plasma vitamin D126 No association milk supplementation‡120, organic food122, dietary anti oxidant123 |
| Respiratory virus infection | |
| Respiratory infection±wheeze | 0.5 (0.3 to 0.9)† for infant lower respiratory tract infection127 9.8 (4.3 to 22.0)* wheeze with rhinovirus128 2.9 (1.2 to 7.1)† wheeze with rhinovirus129 2.2 (1.5 to 3.3)† RSV infection 6–11 months previously130 0.9 (0.7 to 1.0)† early day care132 No association early day care131 |
| Medications | |
| Antibiotics | 1.2 (1.0 to 1.5)†‡ antenatal exposure135 1.5 (1.3 to 1.8)†‡ postnatal exposure135 No association†‡136 |
| Paracetamol | 1.3 (1.1 to 1.4)†‡139 1.2 (1.0 to 1.4)*‡138 No association140 |
| Other medications | 1.1 (1.0 to 1.2) for antibiotics, 1.3 (1.1 to 1.6) gastro-oesophageal reflux treatment, 1.6 (1.1 to 2.3) opiates, 1.3 (1.2 to 1.4) thyroid supplements140 |
| Other maternal exposures during pregnancy | 2.7 (1.2 to 6.0)* dietary dioxins and polychlorinated biphenyl141 2.3 (1.3 to 4.1)* highest vs lowest BPA exposure142 0.7 (0.5 to 0.9)* BPA exposure36 1.1 (1.0 to 1.2)* per 10% increase in DDT metabolite143 1.2 (1.0 to 1.3) for increasing electromagnetic exposure144 |
No effect size and/or confidence intervals were identified for studies with the following citations: 58, 67, 83, 107, 110, 114, 116 and 137.
Magnitude of effect of environmental exposure on respiratory symptoms including wheeze (*), asthma (†), obstructive bronchitis (¶) or atopic disease (¥) in children aged up to 9 years. Details of when the exposure occurred are presented in the text and the supplemental table.
‡Indicates a randomised clinical trial, systematic review or meta-analysis.
BPA, bisphenol A; DDT, dichlorodiphenyltrichloroethane; HDM, house dust mite; LPS, lipopolysaccharide; MVOC, VOC of microbial origin; PVC, polyvinyl chloride; RSV, respiratory syncytial virus; SHS, secondhand smoke; VOC, volatile organic compound.