Vinyl chloride, primarily used in manufacturing PVC plastic, poses significant health risks upon exposure. It's rapidly metabolized in the liver, forming metabolites that can cause liver damage, disrupt cellular functions, and lead to the formation of reactive oxygen species. This can result in oxidative stress and damage to cellular components like DNA, proteins, and lipids. Long-term exposure is notably associated with an increased risk of a rare form of liver cancer known as hepatic angiosarcoma, as well as lung and brain cancers. Acute exposure may lead to symptoms like dizziness, nausea, and headache. Its toxic effects are thus both immediate and delayed, impacting various organs, but with a notable affinity for affecting liver health. Regulatory measures limit occupational exposure, though incidents of accidental release pose significant health hazards.

Titanium dioxide, often used in sunscreens, can potentially harm coral reefs. Studies suggest it can increase the likelihood of coral bleaching, a stress response that can lead to coral death, especially when combined with warming sea temperatures. Titanium dioxide can also react with sunlight and seawater to produce hydrogen peroxide, a compound harmful to all forms of marine life. Therefore, it's recommended to use reef-safe sunscreens that do not contain titanium dioxide when swimming near coral reefs.

To attach PVC pipes together, start by choosing the right size of PVC primer and cement for your pipe. First, ensure the ends of the pipes to be joined are clean and free from debris. Apply PVC primer to the outside of the pipe end and inside the fitting to clean and prepare the surfaces. Once the primer has dried (usually a few seconds), apply PVC cement to the same areas. Quickly join the pipe and fitting together, twisting slightly to ensure an even spread of cement. Hold the joint in place for about 15 seconds to ensure it sets. Allow the joint to cure for the recommended time before testing or using the pipeline, typically 24 hours for full strength.