Plastic waste accumulaties along the Coastal Strip at Panama City Bay, in Panama City, Panama, on August 5. The country has one of the highest annual per capita pollution rates for plastic in Latin America and the Caribbean. (Photo Credit: Carlos Lemos/EPA_

Aug. 11 (UPI) -- Bottles more than 20 years old -- encrusted with marine organisms and worn from long exposure to the sea -- were among the debris collected by the "Científicos de la Basura, or Trash Scientists, network at Chile's Universidad Católica del Norte for a study aimed at determining the origins of plastic waste on Latin American beaches.

After two years of research, the results showed that 59% of the waste analyzed came from the same country where it was found and that Central America's beaches have become the most polluted in the Pacific Ocean by plastic debris -- primarily bottles and loose caps.

The study, published in the Journal of Cleaner Production, also found that coastal communities and beaches in Guatemala, El Salvador, Nicaragua, Costa Rica and Panama had the highest levels of contamination, driven mainly by high domestic beverage consumption and shortcomings in waste management.

However, on oceanic islands such as Rapa Nui in Chile and the Galápagos in Ecuador, most plastic bottles came from multiple countries, including Asian brands -- pointing to transoceanic pollution and discharges from vessels such as cruise ships and industrial fishing boats.

The study focused on plastic beverage bottles because of their abundance and the ease of tracking and collecting them. They often retain key identifying features -- such as product codes, brand names, manufacturing locations and dates -- that help trace their origin and transport routes.

Of all the items analyzed, 26% were manufactured by The Coca-Cola Co., followed by PepsiCo and Grupo Aje, a Peruvian multinational that produces and distributes beverages.

"Since local production plants of multinational companies and single-use plastic bottles are the main contributors to this type of pollution, switching to reusable bottles with a standardized format across the region could substantially reduce plastic pollution along the Pacific coast," the report said.

The study brought together more than 1,000 volunteers from 10 countries on the eastern Pacific coast of Latin America, from Chile to Mexico. They formed teams that received training and conducted standardized sampling at 145 sites in 38 cities, including 92 mainland beaches and 15 oceanic islands, collecting and cataloging more than 21,000 plastic bottles and caps using rigorous citizen science protocols.

"Our results show that plastic bottle pollution is a major environmental challenge that threatens natural ecosystems, and that its reduction and prevention require contributions from governments, producers and communities in all countries, both regionally and globally," said Ostin Garcés Ordoñez, the study's author.

Plastic pollution on beaches is not limited to visible waste such as bottles or containers. Much of the problem is made worse by the presence of microplastics -- tiny particles created when this debris breaks down under the effects of sunlight, waves and wind.

An estimated 1.5 million to 4.5 million tons of microplastics enter the ocean each year, where they can be ingested by marine organisms, enter the food chain and eventually reach human consumption.

These tiny particles have been detected in every ecosystem on the planet -- from the deepest ocean trenches to Arctic ice -- and more recently in the air we breathe, drinking water and everyday foods such as salt and fish.

Australia’s Great Barrier Reef hit by worst coral bleaching on record