BMJ Open · 5 authors, 4 centres
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This systematic review of 40 studies found that charcoal production and usage are linked to adverse health outcomes, most commonly respiratory diseases (21 studies), as well as cancer, DNA damage, carbon monoxide poisoning, and physical injuries. The findings highlight significant health risks for both charcoal producers and users, particularly in low-income settings, and underscore the need for policies to promote safer fuels and occupational protections.
**Background:** Approximately 2.4 billion people globally rely on solid fuels like charcoal for cooking and heating, with charcoal often considered a cleaner alternative to wood. However, charcoal production and combustion release harmful pollutants including carbon monoxide (CO), volatile organic compounds, nitrogen oxides, polycyclic aromatic hydrocarbons (PAHs), and fine particulate matter (PM2.5). These emissions pose health risks, especially in indoor settings and among occupational workers. Despite growing evidence, no prior systematic review had synthesized the health risks specifically associated with charcoal production versus usage. This review aimed to fill that gap.
**Methods:** A systematic review was conducted following a registered protocol (PROSPERO CRD42021213469) and PRISMA guidelines. Searches were performed across MEDLINE, CINAHL, Embase, Web of Science, PsycINFO, Cochrane Library, and SCOPUS from inception to February 26, 2021. Eligible studies were peer-reviewed journal articles reporting empirical findings on associations between charcoal production/usage and health parameters in humans. Excluded were studies on intentional poisoning, combined charcoal with other solid fuels, qualitative studies, animal studies, and grey literature. Two independent reviewers screened, extracted data, and assessed quality using JBI-MAStARI checklists. Due to heterogeneity, a narrative synthesis was performed instead of meta-analysis.
**Key Results:** From 14,032 retrieved papers, 40 studies met inclusion criteria: 8 cohort, 8 case-control, and 25 cross-sectional studies. Most studies (72.5%) were high quality. Studies were conducted across 30 countries, with 56.8% from Africa. Thirteen studies focused on charcoal producers and 27 on charcoal users. The most common health outcome was respiratory disease (21 studies), including asthma (1 study), tuberculosis (1 study), and chronic obstructive pulmonary disease (2 studies). Among charcoal producers, significant associations were found for respiratory symptoms: cough (OR 4.8, 95% CI 1.2–19.7), sputum (OR 6, 95% CI 1.4–26.5), wheezing (OR 7.7, 95% CI 1.4–41.5), and dyspnoea (OR 28.7, 95% CI 5.4–153). Loading kilns was associated with cough (OR 14.1, 95% CI 4.6–43.3) and wheeze (OR 29.5, 95% CI 1.7–516). High cumulative dust exposure was linked to usual cough (OR 2.1, 95% CI 1.1–4.0) and phlegm (OR 2.1, 95% CI 1.1–4.1). Physical injuries were reported in 2 studies, with a 75% injury rate among respondents. DNA damage was associated with urinary mutagenicity (OR 5.31, 95% CI 1.85–15.27). Among charcoal users, respiratory outcomes were also prevalent, with COPD prevalence noted. Charcoal use was associated with increased risk of hypertension (OR 2.61, 95% CI 1.63–4.18), diabetes (OR 2.09, 95% CI 1.17–3.73), stroke (OR 3.17, 95% CI 1.04–9.71), and high cholesterol (OR 1.52, 95% CI 1.04–2.24). CO poisoning and death were reported, with 22 deaths from charcoal used as heating fuel in one study. Cancer studies showed positive associations with lung cancer and oesophageal squamous cell carcinoma. Unintentional weight loss and reduced BMI were observed in women. Sick building syndrome and increased blood pressure were also reported.
**Clinical Implications:** This review provides robust evidence that charcoal production and usage are linked to significant health risks, particularly respiratory diseases, but also cardiovascular, neurological, and genotoxic effects. The findings underscore the need for public health interventions to reduce reliance on charcoal, especially in indoor settings, and to improve occupational safety for charcoal producers. Policies should promote cleaner fuels and enforce protective measures in the charcoal industry. Further research is needed to clarify associations with cancer and other outcomes, and to explore biomarkers and long-term effects.