Neither of those apply here. Missouri statute section 290.145 prohibits an employer from discriminating against an employee “because the individual uses lawful alcohol or tobacco products off the premises of the employer during hours such individual is not working for the employer.” So if the employer took adverse action against the employees for smoking at home, for example, that would violate the statute. Taking action because nurses are taking unauthorized smoke breaks during work hours, on the other hand, is not prohibited.
As far as hostile work environment goes, that has a very particular meaning in the law and isn’t just anything an employee thinks is unfair or doesn’t like. Hostile work environment is a form of illegal harassment in the work place under federal law that is based on the employee’s race, color, national origin, sex, religion, age (if the employee is at least age 40 or older), disability, or genetic test information. So, for example, if an employee was experiencing harassment in the work place related his race that would be illegal. An isolated incident of a racial joke or insult would not be enough, however. As the federal Equal Employment Opportunity Commission (EEOC) explains on its harassment page:
Petty slights, annoyances, and isolated incidents (unless extremely serious) will not rise to the level of illegality. To be unlawful, the conduct must create a work environment that would be intimidating, hostile, or offensive to reasonable people.
Offensive conduct may include, but is not limited to, offensive jokes, slurs, epithets or name calling, physical assaults or threats, intimidation, ridicule or mockery, insults or put-downs, offensive objects or pictures, and interference with work performance.
Here, the employer’s action has nothing to do with the employees’ race, color, national origin, sex, religion, age, disability, or genetic test information. Thus, however unfair you may think it to be, it is not illegal harassment or a hostile work environment as those terms are used in employment. While I think the employer’s choice in taking away breaks as a solution to the problem is unwise, it is not illegal.