Perhaps you've looked into the sky and seen a plane overhead leaving streaks as it flies. For many Americans, these trails are cause for anxiety and anger. People from both left and right-wing groups believe these trails to be linked to a government conspiracy. They believe that the government is intentionally spraying the population with hazardous toxins or attempting to control the weather. They call these trails chemtrails.
The internet is an amazing tool that allows us to access information and discuss our thoughts, connect with like-minded thinkers, and share our opinions with the world. The downside to this, however, is that scores of malicious, and well-intentioned people, can propagate incorrect information that is potentially harmful when taken seriously. It can be confusing, and often frightening to navigate this tangled web in attempts to decipher fact, from fiction.
Leading atmospheric scientists (https://carnegiescience.edu/node/2077) have attempted to assuage suspicions by ensuring the public that chemtrails are in fact a fabrication. Simple geography can easily illustrate that the streamers we see behind an aircraft are nothing more than condensed water and ice crystals. These crystal trails are called a contrail according to Merriam-Webster's Dictionary. It's important to note that the word chemtrail does not appear in the dictionary.
This offers no consolation to conspiracy theorists. They believe that scientists are part of the cover-up and any attempts to refute the existence of chemtrails only creates more animosity in the minds of believers. Conspiracies, such as chemtrails, have a way of evolving organically so any efforts to stamp out these ideas are often ineffective.
A fear of chemtrails appeared in the 1990s after the US Air Force released a report discussing the idea of weather modification. This was an idea to help solve crop die-out, drought and possibly help control natural disasters. By 1999 the internet helped to spread the idea of government mandated cloud seeding, population control and the dumbing down of society using chemical substances sprayed from planes. This was fueled by crop dusters, planes engineered to fly low over crops and release anti-pest dust.
This is a hard question, with an equally difficult answer. No one has the authority to dictate what you do and do not believe. Some people choose to put their faith in logic, science, and trust that the opinions of experts is ethical and correct. Some people choose to reject these ideas.
When trying to decide for yourself it's important to be logical and remember that the best conspiracy theories are so tantalizing because they cannot be proven or disproven. Good science relies on formulating a way to disprove a hypothesis and duplicate an experiment with the same results time and again. This method digs to the core of truth.