Question

(c) The LD₅₀ for DDT is quoted as 500 mg kg^-1

            (i) State what is meant by the term LD₅₀, explaining what the units associated with it mean.

            (ii) The FDA (Food and Drug Administration in the USA) sets a limit of 5 ppm (5 mg kg^-1) for the DDT content of fish. What mass of fish would an adult weighing 80 kg need to consume to reach their LD₅₀, assuming the fish was contaminated to this limit?

                                                                                               

Answer 1

LD50 means "Lethal dose" to kill a half of the animal population test. It is a mesure of the toxicity. It is expressed as mg of substance per kg of the weight of the animal.

For example, if LD50 of DDT is 500mg/kg, it means that 500mg of DDT kills an animal weighing 1kg. Then, 40000mg (40g) of DDT kills an adult weighing 80 kg.

If the concentration of DDT in the fish is 5ppm (5mg/kg), then we need:

of fish.