Which legislation makes it a legal requirement to report adverse reactions to the Medicines and Healthcare Products Regulatory Agency (MHRA).

The question asks which legislation makes it a legal requirement to report adverse reactions to the Medicines and Healthcare Products Regulatory Agency (MHRA).

• The Health and Safety at Work Act 1974 is general legislation for workplace safety and does not specifically mandate reporting adverse reactions to the MHRA.
• The Blood Safety and Quality Regulations 2005 specifically implement EU directives on blood safety and quality into UK law. These regulations include provisions for the reporting of serious adverse events and reactions related to blood and blood components to the MHRA. This is the legislation that directly addresses the reporting requirement for adverse reactions in the context of blood products to the MHRA.
• The Equality Act 2010 deals with anti-discrimination law and is not relevant to reporting adverse reactions to medical products.

Therefore, the legislation that makes it a legal requirement to report adverse reactions to the MHRA, particularly concerning blood products, is the Blood Safety and Quality Regulations 2005.

The final answer is $\text{Blood Safety and Quality Regulations 2005}$