Effects Of Household Environment And Indoor Ventilation On Childhood Airway And Allergic Diseases

In the past 30 years,childhood prevalences of asthma,rhinitis,and eczema（atopic dermatitis）have been sharply increasing in China.Based on a cross-sectional study（questionnaire）and a case-control study（on-site inspection on household environment）of the“China,Children,Homes,Health（CCHH）”study in Shanghai from 2011 to 2014,as well as on a systematic review for literatures which were published from 1985 to 2015,this thesis quantitatively summarized the time-trend prevalences of childhood asthma,rhinitis,and eczema among children in China in the past 30 years;analyzed current status of household environment and indoor ventilation among common residences in Shanghai;and investigated co-effects of household environment（dampness,VOCs,airborne fungi,bed dust mites,and inhalable particle matters）and indoor ventilation with childhood asthma,rhinitis,eczema and other airway and allergic diseases.Based on the systematic review,we found that:prevalences of asthma among infants（0-2-years-old）,preschool children（3-7-year-old）,school-age children（8-12-years-old）,and adolescent children（13-14-year-old）in Shanghai were exponentially increased from1990 to 2011.In 2012,among 3-6-year-old children in mainland China,5.9%（3.5millions）,8.5%（5.1 millions）,and 25.7%（15.5 millions）had asthma,allergic rhinitis,and eczema during lifetime-ever,respectively.Strong co-existence relationships were found among six lifetime-ever diseases（asthma,allergic rhinitis,eczema,pneumonia,ear infections,and food allergy）and among five past-year diseases（wheeze,rhinitis,eczema,dry cough,and common cold）among Shanghai 4-6-year-old children.Based on data from the cross-sectional questionnaire and multiple logistic regression models,this thesis comprehensively analyzed associations of building chatacteristics,early nursing and birth characterstics,lifestyle behaviors,and household dampness-related exposures with nine lifetime-ever diseases（croup,asthma,ear infections,allergic rhinitis,food allergic,eczema,wheeze,pneumonia,and rhinitis symptoms）and five past-year diseases（eczema,dry cough,wheeze,rhinitis symptoms,and common cold（≥3times））among preschool children in Shanghai.Results indicated the following factors had strongly associations with the increased odds of the studied diseases:family history of atopy（averaged odds ratio:2.0）,using antibiotic in the first year of lifetime（1.5）,dampness-related exposures in the current residence（1.4）,dampness-related exposures in the early（during the child’s birth）residence（1.3）,early household decoration（1.2）,and boys（1.2）.Some diseases had significant associations with the child’s age,living close to large industry or heavy traffic road,using oil paints/emulsion paints as materials of wall covering,mother under employed during pregnancy,breastfeeding≤6 months,early household pet-keeping,and early environmental tobacco smoke（ETS）exposures.Parental smoking,indoor incense-burning,and pet-keeping in the current residence had associations with the deceased odds of some studied diseases.Based on data from the on-site inspection as well as non-paramatric test,chi-square test and multiple logistic regression models,this thesis investigated associations of household temperature,relative humidity,dampness-related exposures（10 indicators）,formaldehyde,benzene compounds,airborne fungi,the child’s bed dust mites（Der p1and Der f1）,and inhalable particle matters(PM_1.0,PM_2.5,PM_4.0,PM₁₀)with eleven lifetime-ever diseases（wheeze,croup,asthma,pneumonia,rhinitis,allergic rhinitis,ear infections,eczema,food allergy,dry cough,common cold（≥3 times））and five past-year diseases（wheeze,rhinitis,eczema,dry cough,common cold（≥3 times））among children in Shanghai.The results indicated that:household low temperature could increase odds of asthma and common cold,whereas high temperature could increase odds of pneumonia,rhinitis,and wheeze.High humidity could increase odds of croup,asthma,allergic rhinitis,wheeze,and eczema.Household dampness-related exposures had significant associations with childhood wheeze,croup,asthma,rhinitis,allergic rhinitis,and eczema;herein visible mold in the ceiling and wall covering had strongest associations with these diseases among the 10 dampness-related indictors.Children who were exposured to higher concentration of formaldehyde had higher odds of lifetime-ever wheeze,ear infections,and past-year common cold（≥3 times）.Children who were exposured to higher concentration of benzene compounds had higher odds of lifetime-ever wheeze,croup,asthma,pneumonia,ear infections,eczema,food allergy,and past-year wheeze,and common cold（≥3 times）.Children who were exposured to higher concentration of airborne fungi had higher odds of lifetime-ever wheeze,croup,asthma,and ear infections.Bed dust mites（Der p1 and Der f1）had significant associations with childhood rhinitis,food allergy and dry cough;and herein Der f1 had stronger associations with childhood allergic diseases than Der p1.Children who were exposured to higher concentration of indoor inhalable particle matters had higher odds of lifetime-ever ear infections and past-year wheeze.As in the analyses according to data from the cross-sectional questionnaire,we also found several“uncommon”results:The higher levels the concentrations of indoor pollutants,the lower the odds of some studied diseases.Based on the daily CO₂ concentrations in the child’s bedroom from the on-site inspection,this thesis analyzed night and day air change rates of the child’s bedroom.Taking CO₂ as track-gas,we used build-up method,decay method,and constant method to calculating these ventilation rates.We also calculated the whole-day（24 hours）air change rate via time-weight of night and day air change rates according to the daily trend of indoor CO₂ concentrations.In general,residences with low air change rates were reported more dampness-related indicatiors（moldy odor,visible mold in the wall covering and window pane condensation）;the concentrations of indoor pollutants had decreased trends with air change rate increasing.However,in the winter-inspected residences,concentrations of indoor inhalable particle matters(PM_1.0,PM_2.5,PM_4.0 and PM₁₀)were decreased firstly and then increased with the air change rate increasing（U-type curve）.In the logistic regression analyses,children with higher air change rates had lower odds of asthma,dry cough,and eczema;but there were“uncommon”results:the higher the air change rate,the higher the odds of some studied diseases.In conclusions,family history of atopy,early pet-keeping and home decoration,household dampness-related exposures,and exposures to high concentration of bed dust mites（Der p1 and Der f1）could increase odds of childhood allergic and airway diseases,particularly the family history of atopy,household dampness-related exposures,and exposures to bed dust mites（Der p1 and Der f1）.Improving household ventilation could effectively decrease the odds of most studied diseases for the indoor pollutants exposures.However,during winter when the ambient air quality was bad,excessive improvement of household ventilation instead perhaps increase indoor level of inhalable particle matters.Besides,in logical,the“uncommon”results could be explained by avoidance behaviors in certain risk factors or behavior changes before and after occurance of the studied diseases among families with unhealthy children.Therefore,in the further study,these avoidance behaviors and behavior changes as well as their influences in result-explanations shoud be carefully considered.