Four states in the United States have specific ergonomic regulations in place:

1. California: California has the most comprehensive ergonomic regulations, which require employers to have an ergonomics program in place to address ergonomic hazards and injuries.
2. Washington: Washington has a set of ergonomic rules that require employers to identify and address ergonomic hazards in the workplace.
3. Oregon: Oregon has a set of ergonomic guidelines that are intended to help employers identify and address ergonomic hazards in the workplace.
4. Michigan: Michigan has a set of ergonomic guidelines that are intended to help employers identify and address ergonomic hazards in the workplace.

It is important to note that while these states have specific ergonomic regulations or guidelines in place, all employers are required by federal law to provide a safe and healthy workplace for their employees. The Occupational Safety and Health Administration (OSHA) provides guidelines for employers to identify and address ergonomic hazards in the workplace, even if there are no specific regulations in their state.