"what factors do you think contribute to animals being exposed to toxins? how can individuals prevent exposure? "

Depending on whether the animals are in nature or in a home environment, the factors that contribute to animals being exposed to toxins are man-made. Factories contaminate air and water. Combustion from engines pollutes the air. Garbage that is disposed contaminates the air, water and land. Often times, the lure of food for any animal, is what brings the animal into closer human contact, thus increasing the exposure to toxins. For a pet, the home environment and the decisions the pet owner takes to have chemicals like cleaners, fertilizers or pesticides and like motor oil increase exposure to toxins. 

Individuals can prevent exposure for themselves and their pets by decreasing the use of motor vehicles, reducing the amount of garbage and trash produced, being a informed consumer who attempts to purchase more organic, Earth and animal friendly goods and services. Boycott corporations which contribute to the decline of the environment and increase exposure to these toxins. Other simpler ways, in environments with smog or other industrial pollutants, wearing clothing that covers most of the body, including breathing masks, gloves and glasses or goggles.

Ithink the dna sequences may vary but the amino acid sequences are identical.