As the time neared for the fair to open, foreign newspaper editors wondered about the disease potential from the sewage problems Chicago had long been experiencing. Bad water in 1885, for example, had led to cholera and typhoid epidemics that killed ten percent of the city's population.

Cholera and smallpox were still worries that plagued fair officials at the time of the fair's opening. Most educated people now accepted that polluted water was associated with the outbreaks of diseases like cholera. Since Chicago, despite massive efforts, could still find its water filled with fecal matter and dead cats, fair officials installed their own water purification systems as a safety precaution. They knew that any outbreak of disease associated with the fair would keep people away and ruin the success of their operation. Another plan was to pump pure water in from outside the city and sell it to fair-goers for a penny a cup.

A further problem associated with illness cropped up when Olmstead, a primary designer of the fair, got sick. Whether or not it was, as he contended, arsenic poisoning from the paint in his room, it shows the kinds of environmental hazards people faced on a daily basis. Harry Codman was ill too, with what turned out to be appendicitis.

Lack of sanitation, dangerous materials such as arsenic found in ordinary places, and the difficulty of diagnosing diseases like appendicitis were all hazards that hung over the fair.