A manual telling people how to prevent health damage caused by environmental pollution was issued on Friday, suggesting people stay indoors during hazardous smog.

The book, called "Chinese Citizens' Environment And Health Literacy," was published by the Ministry of Environmental Protection.

It will help spread knowledge of environment-related healthcare and increase people's health awareness, said a statement from the ministry.

Harm caused by environmental pollution is based on the extent to which a person is exposed to hazardous environments, notes the book.

"Outdoor activities should be reduced during hazy day in order to decrease exposure [to harmful particles] and protect health," said Zhu Zhongjun from the Chinese Society for Environmental Sciences, one of the book's compilers.

The book also explains basic skills to prevent lead poisoning, among 30 tips for people to learn.

A study by the Peking Union Medical College and the Chinese Center for Disease Control and Prevention suggests that outdoor and indoor air pollution, which are major sources for airborne particles measuring less than 2.5 microns in diameter, or PM 2.5, are the fourth- and fifth-biggest disease-causing factors in China, respectively. Many blame PM 2.5 for urban smog.

Among the 102 diseases monitored by the World Health Organization (WHO), 85 have been caused by environmental factors, said a WHO report.