Indoor Air Pollution (IAP)

Overview

Indoor air pollution (IAP) also called household air pollution (HAP) in developing countries is a major environmental and public health challenge. According to data from the World Health organisation as many as 4.3 million people died in 2012 as a result of it worldwide. This can be compared with one death every 8 seconds. Most of the death occur in middle and low income countries in South East Asia with 1.69 million death, followed by the Western Pacific regions 1.62 million, Africa 600,000, Eastern Mediterranean region 200,000, Europe 99,000, and in the Americas 81,000 death. In high income countries 19,000 people died because of IAP. IAP/HAP has to be distinguished from outdoor ambient air pollution (AAP) which supposedly caused the death of another 3.7 million people in 2012.
Indoor sources of IAP/HAP are cooking and heating with solid fuels, burning candles or oil lamps, fuel-burning space heaters and tobacco smoke. Of special importance is inefficient and insufficiently vented cooking and heating with solid fuels (biomass and coal) on simple stoves or open fires. Burning these fuels in inefficient stoves results in poor combustion efficiency and high levels of emissions of health-damaging pollutants including both fine and coarse particulate matter, carbon monoxide (CO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and a variety of organic air pollutants (e.g., formaldehyde, 1,3-butadiene, benzene, acetaldehyde, acrolein, phenols, pyrene, benzopyrene, benzo(a)pyrene, dibenzopyrenes, dibenzocarbazoles, and cresols). In a typical solid fuel stove, about 6–20% of the solid fuel is converted into toxic emissions (by mass). The exact quantity and relative composition of the emissions is determined by various factors such as the fuel type and moisture content, stove type and the way the stove and fuel is used by the cook. Most measurements of emissions and the corresponding literature focus on the concentration of particulate matter of different sizes (e.g., PM_2.5, PM₁₀) and carbon monoxide (CO), which are main products of incomplete combustion and are considered to pose the greatest health risk. According to estimations 2.9 billion people used solid fuels (mainly biomass, in the form of wood, charcol, dung, and crop residue) for cooking and other heating purposes in 2012 . Around 80% of them reside in rural and 20% in urban areas. Because much of the burning of solid fuels is carried out indoors in environments with insufficient ventilation, millions of people, primarily poor women and children face serious health risks.

Health Effects

According to WHO there is consistent evidence that exposure to household air pollution is a major risk factor leading to acute lower respiratory infections (ALRI) in children under five, and ischaemic heart disease (IHD), stroke, chronic obstructive pulmonary disease (COPD) and lung cancer (LC) in adults.In addition, the smoke from burning biomass is also causing eye irritations.
Smoke in form of particulate matter with particle diameters of less than 10 micrometers in diameter penetrate deep into the lungs. At sizes of 2.5 micrometers particles can enter the finest parts of the lungs. Ultrafine particles get even into the bloodstream. Exposure to particulate matter has short-term effects such as nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath as well as more severe effects on the respiratory system such as pneumonia and asthma. Children are especially affected by ALRI. A child exposed to smoke in the home is two to three times more likely to catch pneumonia. Globally, pneumonia and other acute lower respiratory infections represent the single most important cause of death in children under five years. Exposure to IAP more than doubles the risk of pneumonia. Women exposed to indoor smoke are three times as likely to suffer from chronic bronchitis and other obstructive pulmonary diseases (COPD) than women who cook and heat with electricity, gas and other cleaner fuels. In addition, there are indications, that indoor smoke is also causing tuberculosis, cataracts, low birth weight and high infant mortality. Most of the victims of IAP are women and children, as they are exposed to the source of indoor smoke and the large associated health risks the most. Women spend daily three to seven hours near the stove with their kids breathing polluted air during cooking. At the early age of the children, when they are newborns or infants, their immature lungs and immune systems make them particularly vulnerable. Over 10 million children aged under five years die every year – 99% of them in developing countries. According to Global Disease Study 2010 the relationship between exposure to pollutants and health effects is often not linear. In the case of PM_2.5 an exposure response model estimating health effects by using relative risk (RR) information for ALRI, IHD,stroke, COPD, and LC is assuming a kind of exponential saturation curve. The health risks rise significantly with increasing concentrations of PM_2.5at lower levels. The effect becomes less pronounced at higher PM_2.5 exposure levels. This has major implications for strategies to reduce health risks by controlling air pollution at high exposure concentration levels.

Regulations and Recommended Maximum Concentrations of PM and CO

Due to the severe health risks of air pollutants, many governments and international organisations have defined maximum concentrations of pollutants for emissions allowed from certain types of pollution sources, for the ambient air (immissions) and for workplaces or short periods of exposure. This chapter only presents the data for PM and CO as they are most widely used to measure the degree of air pollution.
The following table gives an overview about current standards.

Pollutant	Standard	Averaging Time	Country/Region
PM10	150 μg/m³	24-hour	USA
	50 μg/m³	24-hour	EU
	40 μg/m³	annual	EU
	150 μg/m³	24 hrs	China
	70 μg/m³	annual	China
	50 μg/m³	24 hrs	WHO
	20 μg/m³	annual	WHO
PM2.5	35 μg/m³	24-hour	USA
	15 μg/m³c	annual	USA
	25 μg/m³c	annual	EU
	75 μg/m³c	24 hours	China
	35 μg/m³c	annual	China
	25 μg/m³c	24 hrs	WHO
	10 μg/m³c	annual	WHO
CO	35 ppm (40 mg/m³)	1-hour	USA
	9 ppm (10 mg/m³)	8-hour	USA
	9 ppm (10 mg/m³)	1-hour	EU
	10-20 mg/m³	1-hour	China
	35 mg/m³	1-hour	WHO
	10 mg/m³	8-hours	WHO

The table shows a certain variability of the air quality standards in different countries and regions. The variability is mainly caused by different short and long term air quality targets of the countries, the path to obtain these targets considering resources, location, economic structure etc..
In the case of PM2.5 WHO has defined three interim air quality targets for annual outdoor PM2.5., taking into consideration that achieving the full target will not be realistic for most developing countries in a short period of time. The interim air quality targets are: Level 1: 35, level 2: 25, and level 3: 15 μg/m3 per year.

IAP/HAP and Cooking Systems

The term indoor air pollution refers to toxic contaminations of the air in buildings (homes and workplaces). It is identifical with the term household air pollution if referred to the air quality of dwellings. The concentration of pollutants is higher indoors compared to the ambient air pollution, if sources inside the house emit pollutants that do not diffuse rapidly to the outside.

The level of exposure to IAP depends on the air quality in the different rooms or areas in the building and the time a person is spending in the different rooms. In many industrial countries maximum concentrations of pollutants are defined for the air quality at workplaces but not for household situations under diferent denominations such as  AGW (Arbeitsplatzgrenzwerte), MAK (Maximale Arbeitsplatzkonzentration), MAC (Maximaal Aanvaardbare Concentratie) VLEP (Valeur limites d'exposition professionelle), WEL (Workplace Exposure Limits), PEL (Permissible Exposure Limit) and TLV (Threshold Limit Values). An overview about the different regulations are given by the International Labour Organisation on the following website http://www.ilo.org/safework/info/publications/WCMS_151534/lang--en/index.htm. 

In several countries different types of maximum workspace concentrations are defined:

1. maximum average exposure values on the basis of a 8h/day, 40h/week work schedule
   
2. maximum short-term exposure limits for a duration of 1h, 15-30 minutes or less
   
3. maximum absolute exposure limits that should not be exceeded at any time. 
   

Most occupational exposure limits refer to the average values. This means that concentrations can be higher for periods lower than 8 hours. As a general rule: worker exposure levels may exceed 3 times the average level  for no more than a total of 30 minutes during a workday, and under no circumstances should they exceed 5 times the average.  

For respirable dust, which penetrates the alveoles (comparable to PM2.5), occupational exposure limits in industrialized countries generally vary between 1.25 mg/m³ and 5 mg/m^3.. For inhalable dust (comparable to PM10) the respective values are between 10 and 15 mg/m³.

For carbon monoxide, many countries established an average exposure limit of 35 mg/m³. The short-term maximum level for CO is generally higher,  in the UK for example 225 mg/m³.   

Household air pollution caused by using solid fuels and simple inefficient stoves for cooking and heating, and by lighting  homes with kerosene and simple wick lamps, is in many ways comparable to occupational air pollution. Both household practices produce high levels of pollutant emissions in specific areas for a limited period of time during the day. Cooking is generally done 3-4 times a day with a total time of roughly 4 hours. The cook and other people in the kitchen area are exposed to the pollution level at the cooking place only during that time. When leaving the kitchen for the rest of the day they are exposed to air quality situations, where the emissions from the stove are diluted up to a insignificant level. The same is applicable for using kerosene as fuel for lighting. The lights are used for a limited period of time in the evening and early morning in specific rooms. The exposure to pollutants depends again on the length and frequency of a person using these rooms. Generally these are less than 8 hours a day. 

Based on this considerations, average maximum exposure limits of 5 - 10 mg/m³ for respirable dust, of 15 - 30 mg/m³ for inhalable dust and of 70 mg/m³ for carbon monoxide seem acceptable for the 2 billion people which use solid fuels for cooking

The typical 24-hour levels of PM10 in biomass-using homes in Africa, Asia or Latin America range from 300 to 3,000ig/m3. Peaks during cooking may be as high as 10,000ig/m³ especially during the beginning ignition process when combustion is especially incomplete.

Remote rural areas are likely to have better ambient air quality (even when biomass use is higher) than urban or periurban or well-connected rural locations where a more intensive use of commercial fuels and the higher traffic affect stronger the ambient air quality.

WHO Guidelines for Indoor Air Quality and Emission Rate Targets (ERTs)

I can add that later

Reducing Indoor Air Pollution (IAP)

Measures to reduce IAP in developing countries:

• Changes in energy technology Changing the fuel, switching to cleaner alternatives, the so-called BLEENS (biogas, kerosene, liquid petroleum gas(LPG), biogas, electricity, ethanol, natural gas or solar energy)
  
• Improving the design and construction of traditional stoves to improve the combustion (improved stoves, advanced stoves clean stoves) 
  
• Improving the ventilation in the kitchen (smoke hoods that vent pollutants to the outside, ventilation through windows, doors, chimney)
  
• Inducing behavioral changes (using a pot lid when cooking to speeds up the cooking, drying wood before burning it, awareness-raising activities)
  
• Change the living environment (kitchen ventilation)
  

Cleaner Fuels / Improved Cookstoves

The most effective way to reduce smoke in the home is to switch to cleaner fuels (liquid petroleum gas, kerosene or biogas). It’s also possible to improve the air quality and promote energy efficiency and environmental sustainability by promoting improved cooking stoves.

Smoke Hoods

The huge majority of people in developing countries who are still cooking on open fires are often too poor to change to improved stoves and cleaner fuels or have no access to modern combustibles. Where the use of biomass, wood or charcoal remains predominant, and the indoor environment remains subject to high levels of smoke, other alternatives have to be found to improve air quality and related health issues. The installation of a smoke hood can be extremely effective in improving the air quality in houses. This applies especially, when traditional biomass burning stoves are being used without a chimney. In addition, some efficient stoves may not be clean and therefore employing a smoke hood allows for health benefits coupled with lower operating costs. Moreover, in some cultures, an open fire plays a special social role as a place around which the family gathers, traditional meals are cooked or other important rituals. As a result the introduction of improved cookstoves is difficult and a smoke hood serves as the best alternative for improving indoor air quality.

Impacts

Reaching this goal to reduce this extremely harmful IAP would significantly help to achieve several of the internationally agreed Millennium Development Goals, especially Goal 4. Reduce child mortality with the target to decrease by two thirds, between 1990 and 2015, the under-five mortality rate. Since 1990, the mortality rate for children under age five in developing countries dropped by 28% (from 100 deaths per 1,000 live births to 72 in 2008), but not quickly enough to reach the target by 2015. Many organizations are already working on this field to make improvements in this issue.

Further Information

• Smoke Hoods - "Healthy Hoods" Project
• Indoor air pollution in developing countries: a major environmental and public health challenge
• Indoor air pollution (IAP) Measurements
• Health Hoods, Smoke Hoods for developing countries Video (Project by Practical Action and BSH)
• HEDON Hompepage with Video - THese Women's stories tell the cookstoves story
• Hyley in Nepal (The silent killer in Nepal) (Video by Practical Action)