**6. Conclusion**

Fire has always been an enemy of humanity and can cause a lot of destruction. Over time, more and more people live with materials with high flammability, creating the need to control the flammability of these materials. Thus, flame retardants are widely used to reduce the risk of fire, as a safety device. However, other risks can arise


**Table 6.**

*Summary of biological effects caused by organic, halogenated, and inorganic inorganic phosphorus-based flame retardants.*

with the wide use of this class of compounds, including the risks to environmental and human health.

As flame retardants are being used, research and new knowledge are being generated to understand the behavior of these substances in the environment and the consequences for the ecosystem and human health. Classes of flame retardants begin to be legislated and controlled due to their highly toxic potentials, such as PCBs, PBDEs, and HBCD. On the other hand, new compounds have been introduced to

replace the legislated flame retardants, here, phosphorus-based flame retardants emerge as an effective and possibly ecofriendly alternative to the old flame retardants.

As the need arises for alternatives to the old flame retardants, new substances are being introduced into the market with the purpose of reducing the damage that could be caused. However, this insertion occurs without full knowledge of the toxic effects of these new products. Furthermore, over the last decades, we can observe a pattern of substitution of harmful or legislated flame retardants to another that initially was human and ecofriendly but, after few years it turns out and it was harmful. In this way, the environmental consequences can be exacerbated, as can the exposure of ecosystems. In this chapter, we provide a review of the main classes of flame retardants and its possible substitutes, trying to understand the behavior of these substances in the environment and their toxicological consequences for the ecosystem and human health.
