Exposure from cooking with biofuels: pollution monitoring and analysis for rural Tamil Nadu, India

Abstract

In this paper, statistical analysis to examine the links between pollution and the types of kitchen and fuels is carried out for rural houses by first monitoring the indoor air quality (IAQ) followed by regression analysis of 418 households in Tamil Nadu, India. Exposures to the chief cook (females, who are mainly involved in the cooking during monitoring) are measured with personal monitors. The result shows that the values of respirable particles (PM10) ranged from 500–2000 μg/m³ during a two-hour cooking period from burning biofuels. The range depends on the type of kitchen and fuel use. Stationary monitors, placed two metres away from the stove, also recorded similar concentrations. Thus, the individuals who stay inside the houses using biofuels also face high concentrations even if they are not cooking. They could be senior citizens, children or adult males. Thus, there are two major findings from this analysis. Improved house designs that pay attention to kitchen location and put up partitions should also be considered in the intervention portfolio. Secondly, the exposure is not limited to the cooks alone. The rest of the family in the vicinity is also exposed through a “passive cooking effect”.

Introduction

In rural India, 90% of the primary energy use is biomass, of which wood accounts for 56%, crop residues for 16%, and dung-cakes for 21% [1]. Combustion of these bio-fuels in poorly ventilated kitchens using inefficient stoves leads to the release of very high concentrations of suspended particulate matter and noxious gases [2], [3], [4]. Exposure to these pollutants has also been shown in several recent studies to be associated with several health effects especially among women who cook with these biofuels and the young children.

A number of air pollutants — NO_x, SO₂, CO, particulates and ozone — have been identified to be associated with adverse health effects particularly in urban centres of developed countries. However, Smith [5] concentrates on particulates as “the most important single class of air pollutants”. Unprocessed biomass fuels produce 10–100 times more respirable particulate matter than the modern fuels because of their low thermal, combustion and heat transfer efficiencies. Almost in all cases the trend of pollution concentrations is as follows [6], [7], [8]:

$$\text{Dung>Crop}\text{residue>Wood>Charcoal>Kerosene>LPG>Electricity}$$

Raiyani [6] discusses the indoor concentration of Total Suspended Particles (TSP) during cooking hours across the houses belonging to a low socio-economic group in eastern Ahmedabad, India. He concludes that houses using wood, cattle dung and coal emit large amounts of TSP. Particulate matter inside houses using LPG and kerosene are due to the outside environment rather than indoor sources. Ramakrishna [9] tried to establish quantitative estimates of several environmental and cultural characteristics like stove type, kitchen location, and fuel on the TSP exposures. Though the variable location of kitchen was found to be a statistically significant variable, the difference between exposure level using traditional and improved stoves did not prove to be significant. But these results need to be taken with some amount of caution, as the sample size was small. In addition to the factors mentioned above there are several others, which have been identified in the literature to explain the large and significant difference in concentration of Respirable Particulate Matter (RPM) between living area and kitchen while cooking activity is going on — ventilation, chimney type, kitchen volume, outdoor concentrations and so on [2], [4].

Since a large number of variables are involved in the studies of air pollution, it is very difficult to prove that air pollution has a clear demonstrable effect on human health over normal concentrations. However, there is consistent evidence that indoor air pollution due to the burning of biofuels increases the risk of chronic obstructive pulmonary disease, acute respiratory infections among children, cataract, adverse pregnancy outcomes, pulmonary tuberculosis, asthma and cancer [10], [11], [12], [13], [14]. Moreover, most of these studies were observational with small sample sizes (rarely exceeding 200). In the present study we try to address the following questions:

• — What is the level of pollution exposure to chief cooks due to biofuels?

• — What are the levels of pollution concentration in different microenvironments?

• — How serious is the “passive cooking” effect on the non-cooks?

• — Do kitchen location, fuel types and stove types make any significant difference to exposure and concentration levels?