Household use of biomass and lung cancers

INTERIM RESULTS

Imran Choudhury, Dan Pope, Mukesh Dherani, Nigel Bruce

University of Liverpool&

Amir SapkotaUniversity of Maryland

Search strategy• (Lung OR pulmonary OR bronchogenic OR bronchial OR “respiratory tract”

OR bronch* OR trachea* OR “lower respiratory tract” )

• Cancer OR cancers OR carcinoma OR carcinomata OR neoplasm OR neoplasms OR tumor OR tumors OR tumour OR tumours OR “*small-cell”)

• "IAP" OR "Indoor air" OR "pollution" OR "pollutant" OR "fuel" OR "fuels" OR "dung" OR "agricultural waste" OR "crop waste" OR "crop residue" OR "charcoal" OR "coal" OR "biomass" OR "wood" OR "stove" OR "stoves" OR "chula" OR "chulla" OR "oven" OR "ovens" OR "smoke" OR "smoky" OR heat* OR cook* OR light* OR burn*

Databases• PubMed (Medline)• Embase (Scopus & Ovid)• Cochrane Controlled Trials Register• CINAHL (Ovid)• Global Health (Ovid)• DARE (Database of Abstracts of Reviews of Effects) – for reviews• LILACS (Latin American and Caribbean literature)• Scielo• Index Medicus Africanus• Chinese databases CNKI – by Ray Liu @UCB

Search results (English)

• 19,833 search results• 137 papers: full papers (English) or foreign

language paper abstracts with solid fuel data• 60 potentially relevant for biomass review– 25 Chinese abstracts/full papers for Ray– 4 on request /awaiting translation– 17 papers with some form relevant data

Search Results

• Of the 17 papers which have data• All case control studies– 6 combine biomass with another fuel– 11 papers with estimates for meta-analysis– 1/11 later excluded

Excluded from meta-analysis

Exposure

Ramankumar 2006Canada

Combined gas and wood together as traditional fuels. Exclude from M/A.

Shen 1996Nanjing, China

Combines solid fuels into one category. . Exclude from M/A

Shen 2007Xuanwei, China

Combines smokeless coal and wood. Exclude from M/A

Pisani 2006Northern Thailand

Domestic exposure to fumes from coal or wood. Exclude from M/A

Mzileni 1999Northern Province , South Africa

Exposed to wood/coal in house. Exclude from M/A

Chen 1990,Taiwan

Combines wood and coal. Exclude from M/A

Included StudiesSetting Number of studies

India 3 Behera 2005, Gupta 2001, Sapkota 2008

China 2 Gao 1987 (Shanghai), Liu 1993(Guangzhou)

Hong Kong/Taiwan 3 Ko 1997, Koo 1983, Lee 2001,

Japan 1 Sobue 1990

Europe 1 Lissowska 2005,

Mexico 1 Hernandez 2004

Biomass specific exposureAll Indirect Assessment

Wood as current cooking fuel Behera 2005, Gao 1987, Liu 1993

Ever used wood for heating Lissowska 2005, Koo 1983

Ever used wood for cooking Lissowska 2005

Wood for heating or cooking / stratified by years of use

Gupta 2001 (1-45yrs, >45 yrs)Hernandez 2004 (1-20 yrs, 21-50 yrs, >50yrs)Sapkota (0-30, 30-50 and >50 years use)

Cooking fuel used at various stages in life

Sobue 1990; Used wood/grass for cooking at 30 years of age

Ko 1997; Used wood/charcoal vs. gas/no cooking during 3 time periods <20; 20 -40 years age, > 40 years age

Habitual cooking practice Lee 2001; wood/charcoal

Fuel use in reference category uncleare.g. Ever used wood vs. never used wood

Sobue 1990, Gupta 2001, Hernandez 2004, Gao 1987, Koo 1983,

Subjects and Outcome MeasuresSubjects Outcome

Men & Women

Clinically diagnosed Liu 1984

Confirmed lung cancer Sapkota 2008 (80% confirmed, 89% male)Lissowska (71% male)Gupta (88% male)

Women only Clinically diagnosed Koo 1983

Confirmed lung cancer Behera 2005, Sobue 1990, Gao 1987 (80% confirmed), Lee 2001 ( also stratified by histology)

Non-smoking women only

Clinically diagnosed

Confirmed lung cancer Ko 1997

Adenocarcinoma Hernandez 2004

Quality Issues

Selection Exposure Outcome Confounding

Sobue1990Osaka

Use of wood/grass for cooking at the age of 30Unclear what comparison fuels were??

Gupta2001Chandigarh, India

Wood used for cooking or heating but only 12% of controls had never used coal/wood. Therefore comparison is essentially between wood and coal.

Hernandez 2004Mexico City

Record bias- medical records had to document exposure for cases and controls to be selected

Wood for cooking but reference category unclear – author reports probably clean fuel - clarification awaited

Koo 1983Hong Kong(Excluded)

Insufficient information Wood/grassf or cooking but 91% population used thisAlso unclear reference categorys

Not confirmed case No adjustment

Provides OR and p-value only

Quality IssuesSelection Exposure Outcome Confounding

Liu 1993 Current domestic cooking fuel – but only 4.1% used wood

Only 32% confirmed cases

No adjustment

Sapkota 2008India, multi-centre

Wood as cooking fuel but 90% subjects men

All studies (n=10)

Publication bias• Begg's Test• • adj. Kendall's Score (P-Q) = 22• Std. Dev. of Score = 24.28 • Number of Studies = 17• z = 0.91• Pr > |z| = 0.365• z = 0.87 (continuity corrected)• Pr > |z| = 0.387 (continuity corrected)• • Egger's test• ------------------------------------------------------------------------------• Std_Eff | Coef. Std. Err. t P>|t| [95% Conf. Interval]• -------------+----------------------------------------------------------• -------------+------• slope | .0722589 .173642 0.42 0.683 -.2978503 .442368• bias | .4820188 .6609868 0.73 0.477 -.9268412 1.890879

Biomass vs. clean fuel (n=8)

Biomass vs. Clean fuel – excluding weaker studies n=5

Key assumptions/issues

• Unclear reference categories – Ever wood vs. never wood

• Cooking as exposure when most of subjects are men

• Studies with very low population prevalence of biomass use

• Is there a separate pathway for adenocarcinoma?

Issues• Comparable - probably• Valid – a lot of quality issues even before considering

ventilation, behaviour etc

• External validity might help??

• Heterogeneity• Meta-analysis does not give clear answer

• Probably need better data?• Await Chinese studies

Biomass/Lung cancer CRA

Databases: EnglishDatabases: Spanish

Databases: Chinese

Databases searched

Search results filtered

Papers identified & obtained for full review

Data extraction

Independent Quality Assessment

Cross-checking references & citations

Awaited

Meta-analysis Interim results only