pollution

A model has analysed mercury concentrations in rivers around the world from 1850 to the present day. The results, published in Science Advances, conclude that levels have doubled and even tripled since the Industrial Revolution: before 1850, rivers carried approximately 390 metric tonnes of mercury to the oceans each year, and today that figure has risen to around 1,000 metric tonnes. According to the authors, these results have implications for human health and wildlife, as mercury compounds are neurotoxic, can accumulate in fish and pose a health risk through consumption.

A team from the United States has analysed data on modes of transport in more than 11,500 cities in 121 countries around the world, including Spain, representing 41% of the world's population. In addition to studying the factors that most influence the proportion of journeys made on foot or by bicycle, they estimate that if each city analysed increased the extent of its cycling network to the level of Copenhagen (Denmark), private vehicle emissions would be reduced by 6% and the public health benefits would be equivalent to around £37 billion. The results are published in the journal PNAS.

Lead exposure in children can affect their neurodevelopment. In the United States, the maximum blood concentration limit for this metal was lowered to 3.5 μg/dL (micrograms per decilitre) in 2021, down from 10 μg/dL in 2012. Now, a study has analysed data from more than 300,000 children in Iowa and found an association between higher concentrations and poorer school performance in reading and maths, even below the 3.5 μg/dL limit, prompting the researchers to reconsider this figure. The results are published in the journal JAMA Network Open.

Up to 1.4 billion people may be living in areas with soil contaminated by heavy metals such as arsenic, cadmium, cobalt, chromium, copper, nickel and lead, according to research published in Science. The paper, which used data from more than 1,000 studies, estimates that 14-17% of farmland worldwide could be contaminated by at least one toxic metal. Cadmium is the most widespread, especially in South and East Asia, parts of the Middle East and Africa.

In recent decades, the rate of pollen allergies has increased worldwide. One of the reasons being considered is the increase in atmospheric nitrogen pollutants. Now, a study published in the journal The Lancet Planetary Health estimates that grasslands fertilised with nitrogen release six times more pollen and that this pollen is five times more allergenic than that from unfertilised fields.

Research published in Science Advances concludes that the level of microplastics in the environment could be three times higher in 2060 than in 2019, even if one of the two more ambitious policy scenarios proposed by the OECD to reduce plastics is implemented.

Only 9.5% of plastics produced globally in 2022 were generated from recycled materials. The findings, published in Communications Earth & Environment, are part of a comprehensive analysis of the global plastics sector, which also reveals a large increase in the amount of plastic being disposed of by incineration and substantial regional differences in its consumption.

Exposure to mild ozone air pollution during the first two years of life is linked to the development of asthma and wheezing in children between the ages of four and six, both individually and in combination with nitrogen dioxide and fine particles. This relationship was not found in children under eight or nine years old, according to a study published in JAMA Network Open. The epidemiological study is based on data from more than 1,000 children in the U.S.

A study reveals that most of the carbon dioxide (CO₂) absorbed by ecosystems has been stored in dead plant material, soils and sediments, and not in living biomass. These data, which suggest that terrestrial carbon reserves are more resistant and stable than previously believed, are crucial for designing future climate change mitigation strategies and optimising carbon sequestration efforts. The findings are published in the journal Science.

Grass-fed beef is not less carbon intensive than industrial beef, even after correcting for soil sequestration enhancement by rangeland grazing, according to a study published today in the journal PNAS that analysed emissions and livestock data from the United States.