Employers have a responsibility to provide a safe working environment. This is often expressed as a duty of care to employees. This is not a one-way street; employees also have a duty of care to act in a way that does not endanger other employees.
In the case of environmental issues the term due diligence is used. Demonstrating due diligence means taking all reasonable precautions to prevent foreseeable accidents. Having an environmental policy and EMS is a way the company can demonstrate due diligence.
If a case were brought against a company, the courts would ask whether the incident or event was reasonably foreseeable and, if it was, what actions were taken to reduce the likelihood of the incident or event. Penalties may be severe if a discharge of waste is found to be deliberate and the polluter showed a lack of due diligence.