The Hong Kong police force has deployed more than 9,000 rounds of tear gas in the city since June in responding to antigovernment protests.

An estimated 88% of Hong Kong's population resides in affected areas of the crowded city. Of particular concern has been the deployment of tear gas in high-risk enclosed areas such as underground train stations as well as in locations adjacent to vulnerable populations, such as around schools and retirement homes.

On Monday, tear gas was fired near a major hospital close to Hong Kong Polytechnic University where police were battling protesters. Elective operations had to be canceled, ambulances diverted patients to other hospitals and staff reported discomfort after breathing the gas.

The extensive use of chemical irritants in Hong Kong's densely populated neighborhoods and the lack of government-led cleansing and decontamination procedures has generated mounting public concerns about potential short and long-term health effects.

Yet cases of long-term disability or even death from exposure to these chemicals have been documented worldwide. The organic solvents used to dissolve CS can cause skin burns and liver damage, particularly when used in confined spaces.

The intentional incapacitating effects on the respiratory system from these agents can also trigger acute and potentially lethal attacks of asthma or bronchitis in susceptible people, particularly in the hot and humid subtropical environment of Hong Kong.