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close this book Boiling Point No. 30 - April 1993
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Smoke Gets in your Eyes-and Forms Cataracts

Reproduced with the kind permission from Down to Earth November 30 1992

The oxidising property of cigarette and chulha smoke is one of the factors being linked by researchers to the formation of eye cataract.

Inhalation of cigarette and chulha smoke could be a major cause of Indians developing cataract sooner than people in the developed world. Scientists V K Shalini, Mani Luthra and D Balasubramanium of the Centre for Cellular and Molecular Biology (CCMB) at Hyderabad and Leela Srinivas from the Food Technology Research Institute in Mysore say smoke from cigarettes and chulhas hastens cataract formation.

Cataract, or opacity of the eye lens, is a major cause of blindness in India. In a joint Indo-US study, Madan Mohan of the Rajendra Prasad Centre of Ophthalmic Sciences in New Delhi has identified a number of factors that accelerate cataract. These include exposure to sunlight; deficiency of vitamins A, C, and E; high smoky, cooking fuels such as wood, charcoal and dung and smoking cigarettes and beedis.

The eye lens is made up of proteins known as crystalline that impart transparency to it. The lens is metabolically inert, which means it does not regenerate once damaged. Modifications to the crystalline, therefore, accumulate over time.

The team led by Balasubramanium, who is director of CCMB, unravelled the mechanisms of cataract formation and found that crystalline oxidised on exposure to light and other oxidising agents, generated by cigarette and chulha smoke. When this happens, the highly-ordered, spaghetti-like crystallin molecules are reduced to an insoluble mass, turning the lens opaque.

Says Balasubramanium, "We were initially uncertain whether smoke acted by penetrating the lens or after inhalation and absorption by body fluids. But now we are fairly certain the latter is true". The lens is well protected from outside influences by the cornea - the circular window in front of the eye and the lens capsule that holds the lens in place. When cigarette or chulha smoke is inhaled, the aromatic hydrocarbon compounds in it get metabolised and release oxidising agents, which are activated by light and cause the crystalline to precipitate.

The CCMB scientists incubated rat lenses in cigarette smoke solution for about 10 hours and found the worst damage in the lens not treated by antioxidising agents and most exposed to light.

Though smokers and overworked housewives are more likely to develop cataract, they can prevent it by consuming anti-oxidising, vitamin C-rich foods such as amla and some leafy vegetables, says Balasubramanium. Shalini and Srinivas also have found a compound in turmeric that may help prevent damage.



Fuel Efficient Cookstoves Using Cow Dung Cakes-

A study sponsored by CORT and made by Dr Rajendra Prasad, Centre for Rural Development and Appropriate Technology, IIT, New Delhi

Reproduced from Changing Villages: Rural News and Views Vol. 11 No. 2 April-June 1992

In India, there are basically two major designs of metal stoves for burning cow dung cakes. Both were studied and the lessons learnt were as follows:

1. There has to be a proper and sufficient supply of primary and secondary air for the efficient combustion of the fuel and the volatiles generated. Care has to be taken that the ash created by the combustion of the cowdung cakes does not restrict the flow of primary air. It should be possible to remove the ash as and when it is formed.

2. The firebox size, both in terms of its height and diameter (width) has to be large enough to accommodate enough fuel to last the total cooking period desired. This does not mean that all the fuel required is fed at the beginning. It can be fed in batches to ensure that there is a continuous building up of the fuel inside the stove. The firebox has to be designed to accommodate this accumulation of the burning fuel.

3. Cowdung as a fuel is very different from wood. Its combustion is different; it is much more bulky, the ash content is large, and the volatile content is large. The carbon content is lower, the burning ratio is lower and the ratio of primary to secondary air needed is different. The temperatures generated and the I lame size and patterns arc different. All these things must be kept in mind when designing a stove for efficient combustion of cowdung is, therefore, obvious that a stove designed to be efficient for the combustion of wood may not perform so well with cowdung cakes. Certainly one can try lo achieve some sort of optimal conditions by designing a stove for mutifuel combustion.

Based on the above understanding, an attempt was made to design a stove for efficient combustion of cowdung cakes. This does not mean that the stove cannot take other fuels, say wood, but that has not been the main objective here. That will be dealt with in a separate study. The objective here has been very clearly defined.




This is a metal stove, easily transportable, strong and sturdy, easy to handle, safe to operate, much

less smoky, fast and efficient burning, not too costly (about 200 Indian rupees (USA) for the large size and about 15() Indian rupees (US$6) for the medium one).

This is in a way a double walled cylindrical stove, the outer wall is a thin plain sheet metal one while the inner one carries several rows of small (a few mm dia) holes. The 2mm gap between the walls is open towards the bottom of the stove while the top is sealed. The grate is made of 0.5 cm thick iron rods, at 0.5 cm spacing having about the same amount of spacing between them. The stove is provided with legs, handles and pot supports. It is simple to manufacture in any village sheet metal workshop. All the materials of construction are available in the market without difficulty. No special skill is required to manufacture or to use it.

Technical Design

The gap between the two walls has a double function. One, is to act as an insulator reducing the heat losses to the atmosphere. This results in higher temperatures inside the firebox, easy ignition and more complete fuel combustion.

Second, the hot air in the gap is drawn through three rows of small holes in the firebox wall to supply hot secondary air which is extremely useful for the efficient combustion of the fuel and the volatile generated. Clear blue flames appear at those holes where the hot air meets the volatile gases.

The grate supplies the required primary air for the combustion of the fuel and allows the ash to fall down without choking the air flow. This type of grate is not needed for wood fuel as the ash content is much lower and such large spacings create too much free space causing heat losses, cooling off the fuel and reducing temperatures inside the fuel thus causing difficulties in the ignition of the fuel.


The performance of the stove is very good. It reduces the smoke output, which is normally bad with cowdung fuel, makes lighting up easier, needs less attention and reduces the risk of the fire going out when re-fueling. Over feeding or under feeding or delays in feeding do not cause the fire to go out immediately. The control and range of operation of the stove at low power outputs and high power outputs is improved. The long steady flames generally visible with wood combustion are a rare sight with cowdung cakes. In this stove, cowdung cakes almost compete with the wood in this regard. The high volatile content generally found a nuisance during combustion by causing intense smoke has been converted to an advantage by burning after mixing with preheated secondary air.


There is a gain both in terms of better combustion efficiency of the fuel and better heat transfer to the vessel. Assuming a net calorific value of 2500 kcal/kg for the cowdung cakes, efficiency over 30% has been achieved for the large sized stove (suitable for cooking around 10 kg of material at a time) and over 20% for the medium sized stove of about half that capacity. Cooking is quicker and pans are cleaner.

Ed Note: Many developing countries do not have the quantities of cowdung available in India and so would not have use for these Chulhas. as. However, the procedure described and the basic principles of combustion involved are instructive. There may be other biomass residues which can be burnt in stoves designed in a similar way.

Solar Pond Method to Heat Water

Reproduced from Science for Villages, June -September 1992/25

The BVB engineering college Hubli, in collaboration with the Karnataka State Council for Science and Technology, Indian Institute of Science (IISC), Bangalore and the Department of NonConventional Energy Sources, New Delhi, has constructed a solar pond which has been meeting the needs of nearly 400 hostelites.

It is 2.15 metres deep with inner sides sloping at 45 degrees. It is lined with low-density polythene to prevent seepage. Tiles are fitted to protect the lining. About 100 tonnes of common salt is stored at the bottom of the pond and water is let in to a height of one metre, which is the lower zone.

In an ordinary pond, hot water at the bottom is lighter and hence rises to the top and mixes with the rest of the water body. Hence, the temperature is not much higher than the outside temperature. In a solar pond, the hot water at the bottom is not allowed to rise as it is made heavier by adding salt. A solar pond can deliver water which is 50 to 90 degrees centigrade hot. It can be used for hospitals, dairies, hostels and a few industries.

The difference between the conventional solar collectors and the solar pond, according to Prof. Ramannavar, is that the former is expensive, as materials like glass, copper, aluminium and glasswool are used and yet does not have the capacity to store the energy, while the latter is economical as water is used as the medium for absorption and storage with ground as the insulator, which acts as built-in storage. With this advantage, the solar pond can deliver hot water even on cloudy days for about ten days.

The total cost of the project was around Rs. 3 lakh. An amount of Rs.5000 per month is saved on the cost of firewood, which was being used for the purpose. It also prevents denudation of forests in about 70 to 100 acres of land. Above all, this system is pollution-free. The life of a solar pond is expected to be around 20 years.

Source: Times of India