Union carbide accident safety policies and procedures were not followed was due to

Defects in design, maintenance letdowns, lack of training, economy dealings, and blunders in operations.  

Explanation:

The design definitely was not appropriate, and there was lack in maintenance. Also there was lack of training, and blunders in operations. The project was not sound economically as well. And, you should know that problem arose due to water leakage. And that was due to mainly maintenance failure, which you can study in deep through Material Science. Lack of design is part of industrial design and others are part of management.

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