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Combined household water treatment and indoor air  pollution projects in urban Mambanda, Cameroon and rural  Nyanza, Kenya 

Using the gradient method, element concentrations within the lichen are usually observed to increase as the distance to the suspected source decreases. Gough and Erdman (1977) used linear regression to evaluate the relationship between distance from a coal fired power plant and metal levels in Xanthoparmelia chlorochroa. However, as Puckett (1988) points out, concentrations of many elements will not reach zero at large distances from pollution sources because they have essential nutritional roles or are normal components of the lichen when growing in its natural environment. In the Mt Zirkel study mentioned above, three species of lichen. | WHO SDE 02.11 English only World Health Organization Combined household water treatment and indoor air pollution projects in urban Mambanda Cameroon and rural Nyanza Kenya Geneva 2011 Photo credit Bruce N and Shaheed A 2009 Combined household water treatment and indoor air pollution projects in urban Mambanda Cameroon and rural Nyanza Kenya World Health Organization 2011 All rights reserved. Publications of the World Health Organization can be obtained from WHO Press World Health Organization 20 Avenue Appia 1211 Geneva 27 Switzerland tel. 41 22 791 3264 fax 41 22 791 4857 e-mail bookorders@who.int . Requests for permission to reproduce or translate WHO publications - whether for sale or for noncommercial distribution - should be addressed to WHO Press at the above address fax 41 22 791 4806 e-mail permissions@who.int . The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country territory city or area or of its authorities or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement. The mention of specific companies or of certain manufacturers products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted the names of proprietary products are distinguished by initial capital letters. All reasonable precautions have been taken by the World Health Organization to verify the information contained in this publication. However the published material is being distributed without warranty of any kind either expressed or implied. The responsibility for the interpretation and use of the material lies with the reader. In no event shall the World Health Organization be liable for .