Advanced imaging with CT shows that people who cook with biomass fuels like wood are at risk of suffering considerable damage to their lungs from breathing in dangerous concentrations of pollutants and bacterial toxins, according to a poster at the annual meeting of the Radiological Society of North America (RSNA).
Approximately 3 billion people around the world cook with biomass, such as wood or dried brush. Pollutants from cooking with biomass are a major contributor to the estimated 4 million deaths a year from household air pollution-related illness.
While public health initiatives have tried to provide support to transition from biomass fuels to cleaner-burning liquefied petroleum gas as a fuel source, a significant number of homes continue to use biomass fuels. Financial constraints and a reluctance to change established habits are factors, combined with a lack of information on the impact of biomass smoke on lung health.
"It is important to detect, understand and reverse the early alterations that develop in response to chronic exposures to biomass fuel emissions," said study co-author Abhilash Kizhakke Puliyakote, a postdoctoral researcher from the University of California San Diego School of Medicine.
A multidisciplinary team led by Eric A. Hoffman, at the University of Iowa, in collaboration with researchers from Periyar Maniammai Institute of Science and Technology, investigated the impact of cookstove pollutants in 23 people cooking with liquefied petroleum gas or wood biomass in Thanjavur, India.
The researchers measured the concentrations of pollutants in the homes and then studied the lung function of the individuals, using traditional tests such as spirometry. They also used advanced CT scanning to make quantitative measurements – for instance, they acquired one scan when the person inhaled and another after they exhaled and measured the difference between the images to see how the lungs were functioning.
Analysis showed that the ones who cooked with wood biomass were exposed to greater concentrations of pollutants and bacterial endotoxins compared to liquefied petroleum gas users. They also had a significantly higher level of air trapping in their lungs, a condition associated with lung diseases.
"Air trapping happens when a part of the lung is unable to efficiently exchange air with the environment, so the next time you breathe in, you're not getting enough oxygen into that region and eliminating carbon dioxide," Dr Kizhakke Puliyakote said. "That part of the lung has impaired gas exchange."
The researchers found a smaller subset of the biomass users who had very high levels of air trapping and abnormal tissue mechanics, even when compared to other biomass users. In about one-third of the group, more than 50% of the air they inhaled ended up trapped in their lungs.
"This increased sensitivity in a subgroup is also seen in other studies on tobacco smokers, and there may be a genetic basis that predisposes some individuals to be more susceptible to their environment," Dr Kizhakke Puliyakote said.
CT added important information on smoke's effect on the lungs that was underestimated by conventional tests.
"The extent of damage from biomass fuels is not really well captured by traditional tests," Dr. Kizhakke Puliyakote said. "You need more advanced, sensitive techniques like CT imaging. The key advantage to using imaging is that it's so sensitive that you can detect subtle, regional changes before they progress to full blown disease, and you can follow disease progression over short periods of time."
The lack of emphysema in the study group suggests that exposure to biomass smoke is affecting the small airways in the lungs, Dr. Kizhakke Puliyakote said, although more research is needed to understand the disease process. Regardless, the study results underscore the importance of minimising exposure to smoke. Even in the absence of overt symptoms or breathing difficulties, the lung may have injury and inflammation that can go undetected and potentially unresolved in some people.
"For people exposed to biomass smoke for any extended duration, it is critical to have a complete assessment of lung function by health care professionals to ensure that any potential injury can be resolved with appropriate interventions," Dr. Kizhakke Puliyakote said.
While the study focused on cooking with biomass, the findings have important implications for exposure to biomass smoke from other sources, including wildfires.
"In conjunction with the increasing prevalence of biomass smoke due to wildfires in the U.S., this study can provide valuable insights regarding similar study designs serving to understand what is certain to be a growing assault on lung health."
Correlation Between Imaging and Environmental Factors in a Population of Cooks Using Biomass Fuels
We sought to characterize the impact of cookstove pollutants in a rural population, using quantitative computed tomography (QCT) and in-home assessments of environmental exposures.
METHOD AND MATERIALS
We assessed the homes of 21 subjects cooking with LP gas or wood biomass. Environmental assessments included real-time PM<=2.5μm (PM2.5) concentrations, black carbon, sediment mass, and endotoxin level. Large particulate matter was analyzed for metal composition and applied to human airway epithelial cells in culture to measure in-vitro airway cell permeability. QCT was performed via a GE Optima 128 slice scanner utilizing a standardized protocol at coached total lung capacity (TLC) and residual volume (RV). Image analysis included air trapping derived from a disease probability map (VIDA Diagnostics), Mean Jacobian, and a local anisotropic deformation index (ADI). k-means clustering using image-based metrics was applied to classify subjects into two groups. Posthoc analysis was used to identify environmental predictors influencing differences between the clusters.
Biomass cooks had significantly higher %air trapping (36.3 ± 28.3% vs. 20.8 ± 11.6%, p=0.05) and increased exposure to PM2.5 (129.6 ± 177.1μg/ml vs. 39.5 ± 13.3μg/ml, p=0.05) and endotoxin concentrations (2.1±1.8 vs. 0.5±0.1 x106 EU/m2, p<0.01). Strong pairwise correlations were observed between imaging metrics (Jacobian mean, ADI mean, and Percent Air trapping), and environmental factors (PM2.5, total rug mass, endotoxin concentration, and concentrations of Chromium, Radium, Sulphur, and Rubidium). Clustering generated a subset of 5 subjects with significantly altered lung function as defined by image metrics. Post-hoc analysis identified cell permeability, black carbon, and endotoxin concentration as top environmental markers with Sulphur, Uranium, Strontium, and Niobium demonstrating greatest prediction potential among metals.
Subjects cooking with biomass experience greater alterations in image-based metrics of lung function. Using a subset of potentially vulnerable subjects, the environmental markers with greater prediction potential have been identified, independent of fuel type.
With the CT-based phenotyping of the lungs and characterization of associated environmental markers, solutions for disease mitigation will be better informed.
Full RSNA release and video