Titanium dioxide and zinc oxide are widely used in various products, especially sunscreens, due to their effectiveness in blocking harmful UV radiation. The U.S. Food and Drug Administration (FDA) considers both compounds to be generally safe for use in over-the-counter sun-protection products. Zinc oxide is a mineral that provides broad-spectrum UV protection by reflecting sunlight, thus preventing it from penetrating the skin. Titanium dioxide also acts as a physical barrier against UV radiation but is less effective against long-wave UVA rays compared to zinc oxide. Despite their safety profile, some concerns have been raised about the potential for inhalation of these substances in powder or spray form, which could pose health risks. The FDA has suggested using creams or lotions as safer alternatives. Additionally, nano-sized particles of these substances have been developed for use in sunscreens, which some studies suggest could penetrate the skin and cause cellular damage. However, current research generally supports the safety of nano-sized versions when used in skin applications.

1. Passenger Cars: Almost all modern passenger cars contain a catalytic converter to reduce harmful emissions.
2. SUVs and Trucks: These larger vehicles also come equipped with catalytic converters for the same reasons.
3. Motorcycles: Even motorcycles, including both petrol and diesel models, use catalytic converters.
4. Buses: Including city buses, school buses, and long-distance coaches, almost all buses are equipped with catalytic converters.
5. Vans: Both passenger and commercial vans typically have catalytic converters.
6. Construction machinery: Heavy machinery and equipment used in construction often have catalytic converters.
7. Generators: Many generators, especially those run on diesel, contain catalytic converters.
8. Forklifts: Catalytic converters are common on forklifts as well, especially those used indoors.
9. Recreational Vehicles (RVs): These vehicles also use catalytic converters to control emissions.
10. Boats: Certain boats, especially those that are intended for use on inland waters, may also contain catalytic converters.
Remember, the primary purpose of a catalytic converter is to reduce harmful emissions from a vehicle's exhaust, which is why they are found in any internal combustion engine including petrol, diesel and even hybrid vehicles.

In most cases, a car will not pass inspection with the check engine light on due to emission test failures. The check engine light signals an issue within the vehicle's emission control system or other critical components. Since emissions inspections assess a vehicle's adherence to environmental standards by evaluating the exhaust gases, any malfunction causing the check engine light to come on might result in failure. However, the exact impact depends on your location, as inspection criteria vary. It's advisable to diagnose and repair the underlying issue triggering the check engine light before your inspection. Not only does this increase your chances of passing, but it also ensures your vehicle operates efficiently and safely.