A cross-sectional epidemiological method was adopted to investigate the four main urban …

• Abstract
• Background
• Results and discussion
• Conclusion
• Methods
• Miscellaneous
• References
• Table 1
• Figures

Competing interests

The author declares that they have no competing interests.

About the author

Dean of Admission and Registration, Najran University; Supervisor of ITC, eLearning and Training Centre; Academic Accreditation Centre, 2006-present, Najran University, Post Office Box: 1988, 11001, Najran, Saudi Arabia.

Acknowledgements

The author would like to express his thanks to the Administration of King Khalid University for meeting logistic needs, as well as to his colleagues, staff, and his postgraduate students of the Geography Department, School of Human Sciences (i.e., PG: M S Dh. AlSalim was supervised partially by the author) and the Department of Applied Medical Sciences Laboratories, Khamis Mushait Community College, King Khalid University, for their help and support and useful advice during the course of this study. Special thanks are due to MSA Zaki, Professor of Epidemiology and Environmental Health and Chairman of the Department of Applied Medical Sciences Laboratory, and his colleagues, for their help in analysing and interpreting the study samples. Finally, conclusions contained herein are those of the author, based upon the study's findings, and should not be interpreted as necessarily representing either regional and/or national official policies or endorsement, or as expressing or implying the interests of any organisation or any person connected with them. Last but not least, my appreciation also goes to the anonymous reviewers for their useful comments.