Generally. titanium dioxide is regarded as safe for use on the skin and is commonly used in sunscreens due to its excellent UV ray protection. The use of large. non-nanoparticle titanium dioxide formulations has been recommended due to concerns about nanoparticles' effects on human health.

Sealing PVC threads to metal requires careful consideration to prevent leaks. Start by cleaning both the PVC and metal threads to remove any debris. Apply a liberal amount of PTFE (Teflon) tape specifically designed for plastic-to-metal applications, wrapping it around the PVC threads in the direction of the thread spiral to ensure it stays in place when you thread the pieces together. For additional sealing, consider using a pipe thread sealant suitable for both PVC and metal, applying it over the tape. These sealants often come in a liquid or paste form and help fill any gaps that the tape might not cover. Carefully thread the PVC into the metal, avoiding over-tightening which can cause damage to the PVC threads. After assembly, allow any sealant used to cure according to the manufacturer's instructions before pressurizing the system.

An oil grade refers to the classification of an oil's viscosity and performance characteristics, established by industry standards to determine its suitability for various engines or machinery. Viscosity, a key property, measures the oil's resistance to flow. The Society of Automotive Engineers (SAE) sets the oil viscosity grades, such as 5W-30, where the first number followed by "W" (winter) indicates the oil's flow at cold temperatures, and the second number indicates its flow at high temperatures. Higher numbers mean thicker oil. Choosing the correct oil grade ensures optimal engine performance, efficiency, and longevity. Other classifications like API (American Petroleum Institute) and ACEA (European Automobile Manufacturers Association) further define oil performance in terms of engine protection, fuel economy, and emissions standards.