Tell you husband your concerns are well-founded. Some chemicals (naturally derived or synthetic) can develop toxic levels in humans and pets.
Depending upon the pet (usually smaller pets: cats and smaller) certain chemicals can concentrate in the liver and other organs.
Just because a product is "natural" does not mean it cannot be potentially harmful to you or your pet.
There is still much controversy surrounding "toxicity" in natural products (i.e. vitamins or essential oils) for humans but especially small pets (i.e. cats).
The key is to understand the difference between the physiology of animals and humans. Humans metabolize certain types of fats and chemicals differently. Generally, it is the "accumulation" of unprocessed chemicals that adds to the problem.