The ADA does not override health and safety requirements established under other federal laws even if a standard adversely affects the employment of an individual with a disability. If a standard is required by another federal law, an employer must comply with it and does not have to show that the standard is job related and consistent with business necessity.
For example, employers must conform to health and safety requirements of the U.S. Occupational Safety and Health Administration. However, an employer still has the obligation under the ADA to consider whether there are reasonable accommodations, consistent with the standards of other federal laws, that will prevent exclusion of qualified individuals with disabilities without violating the standards of those laws. If an employer can comply with both the ADA and another federal law, then the employer must do so.
The ADA does not override state or local laws designed to protect public health and safety, except where such laws conflict with ADA requirements. If there is a state or local law that would exclude an individual with a disability from a particular job or profession because of a health or safety risk, the employer still must assess whether a particular individual would pose a "direct threat" to health or safety under the ADA standard. If such a "direct threat" exists, the employer must consider whether it could be eliminated or reduced below the level of a "direct threat" by reasonable accommodation. An employer cannot rely on a state or local law that conflicts with ADA requirements as a defense to a charge of discrimination.