cumulative

In the middle of July, Americans along the East Coast and in the Midwest suffered through a massive heat wave that saw actual temperatures soaring and so-called feels-like temperatures go much higher. The punishing heat had many of us reaching for those plastic water bottles all day long as we tried to keep hydrated.

Studies have shown that those single-use plastic bottles do not handle the heat very well. Most plastic items release tiny amounts of chemicals into the beverages or food that they contain. But the hotter it gets, the more the substances in plastic can move into food or drinking water. As temperature and time increase, the chemical bonds in plastics increasingly break down and chemicals are more likely to leach.

A study at Arizona State University in 2008 looked at how heat sped up the release of the element antimony in bottles made of the common plastic PET. Antimony is used to manufacture the plastic and can be toxic in high doses. At mild temperatures, very little antimony is released. But PET and other plastics can leach a variety of chemicals when exposed to higher temperatures.

According to the FDA, the amounts of chemicals released by plastics are too miniscule to cause health problems. However, scientists are still looking at the long-term effects of using so much plastic. The question is whether all those small doses can eventually add up to something not so harmless. Given that we don’t really know the cumulative effect of being surrounded by plastics in the goods we buy as well as the presence of microplastics in our water, it seems like a good idea to try to limit our exposure when alternatives are available.

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Exposed to extreme heat, plastic bottles may ultimately become unsafe

Photo, posted June 7, 2013, courtesy of Tim Stahmer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

There are sizeable numbers of people who hold to beliefs that run counter to overwhelming contrary evidence. Flat Earthers and Holocaust deniers are well-known examples and, more recently, people – some of them in high places – who reject the evidence for climate change.

New research published in the journal Open Mind by developmental psychologists at UC Berkeley suggest that feedback, rather than hard evidence, boosts people’s sense of certainty when learning new things or trying to tell right from wrong. People’s beliefs are more likely to be reinforced by the positive or negative reactions they are exposed to than by logic, reasoning, and scientific data.

People’s learning habits can limit one’s intellectual horizons. According to the study, if you think you know a lot about something, even though you don’t, you’re less likely to be curious enough to explore the topic further and will fail to learn how little you know.

This phenomenon plays out in social media and cable-news echo chambers and explains how some people are easily duped by charlatans. Receiving positive feedback for what they are saying can make people believe they know more than they actually do. This confidence makes them less likely to seek out and learn more information about the subject, as well as take into account contradicting opinions or facts.

Another factor is that what influences people’s certainty is that their confidence tends to depend on what they heard most recently rather than on long-term cumulative data. A few pieces of recent information tend to get much more attention than an extensive body of data. If a crazy theory is able to make a correct prediction a few times, people tend to get fixed in their belief in that theory and be less open to other information.

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Here’s Why People Advocate False Beliefs, Conspiracy Theories Despite Evidence

Photo, posted February 2, 2007, courtesy of Tim J. Keegan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.