Titanium dioxide is a common additive in many products, including food and cosmetics, due to its brightness and strong adhesion properties. According to the FDA, it's considered a safe substance for general use. However, it is inadvisable to intentionally feed this to your dog or any pets as their bodies may react differently than humans. It's not associated usually with toxicity in dogs, but could potentially cause digestive upset, especially in larger amounts. Keep in mind that pet food and treats do not require coloring or additives for nutritional needs, and natural options are always best. In sum, titanium dioxide isn't notably harmful for dogs but should not be intentionally introduced into their diets.

Polypropylene by itself is generally considered compliant with California's Proposition 65, also known as the Safe Drinking Water and Toxic Enforcement Act of 1986. This is because polypropylene, a type of plastic identified by recycling code #5, does not inherently contain substances at levels known to cause cancer, birth defects, or other reproductive harm, which Prop 65 is designed to protect against. However, it's essential to note that the compliance of a polypropylene product also depends on any additives or chemicals used in or on the product during manufacturing. Manufacturers are responsible for ensuring their products are Prop 65 compliant, which may involve reformulating products or providing clear warnings if harmful chemicals are present above safe harbor levels set by the California Office of Environmental Health Hazard Assessment (OEHHA).

Yes, you can glue rubber to PVC by using an appropriate adhesive designed for both materials. Cyanoacrylate (super glue) or a specialized polyurethane adhesive are commonly recommended for bonding rubber to PVC due to their strong bonding properties and resistance to water and temperatures, which are crucial for the longevity of the bond in various environments. Surface preparation is key; ensure both the rubber and PVC surfaces are clean, dry, and roughened slightly to improve adhesion. Applying the adhesive thinly and evenly on both surfaces, and allowing it to cure for the recommended time, will result in a robust bond.