The life expectancy gap between America's rich and poor is shrinking for the young, a new study reports.

In fact, life expectancy at birth has been improving for virtually all income groups born in 1990 onward. The results reveal that many of the U.S. policies directed at improving the health of the young and the poor may have been successful. Previous research suggests that disparities in mortality inequality have widened since the start of the 21st century - with Americans in the top income bracket gaining several years of life expectancy while those at the bottom have gained almost nothing, or even experienced a life expectancy decline.

Managers who inspire their staff to perform above and beyond the call of duty may actually harm their employees' health over time, according to researchers from the University of East Anglia (UEA).

The findings suggest that constant pressure from these 'transformational leaders' may increase sickness absence levels among employees. They also indicate that some vulnerable employees in groups with transformational leaders may in the long term have increased sickness absence rates if they ignore their ill-health and frequently show up for work while ill, known as presenteeism.

A new test has been developed to check for contamination of shallow groundwater from modern gas extraction techniques, such as hydraulic fracturing, commonly known as fracking.

A century ago, more than 60,000 tigers roamed the wild. Today, the worldwide estimate has dwindled to around 3,200. Poaching is one of the main drivers of this precipitous drop. Whether killed for skins, medicine or trophy hunting, humans have pushed tigers to near-extinction. The same applies to other large animal species like elephants and rhinoceros that play unique and crucial roles in the ecosystems where they live.

Human patrols serve as the most direct form of protection of endangered animals, especially in large national parks. However, protection agencies have limited resources for patrols.

Plastics are all around us. They are found in containers and packing materials, children's toys, medical devices and electronics.

Unfortunately, plastics are also found in the ocean.

A 2015 paper published in Science estimates that anywhere from 4.8 million to 12.7 million metric tons of plastic were dumped into the ocean in 2010 alone. One metric ton equals approximately 2,200 pounds, roughly the weight of a Mazda Miata.

As we celebrate Earth Day on Friday, April 22, new research by University of Delaware physical oceanographer Tobias Kukulka provides evidence that the amount of plastic in the marine environment may be greater that previously thought.

Gender stereotyping may start as young as three months, according to a study of babies' cries from the University of Sussex.

Adults attribute degrees of femininity and masculinity to babies based on the pitch of their cries, as shown by a new study by researchers from the University of Sussex, the University of Lyon/Saint-Etienne and Hunter College City University of New York. The research is published in the journal BMC Psychology.

• Adults often wrongly assume babies with higher-pitched cries are female and lower pitched cries are male