There is a growing body of evidence that many of the thousands of prescription and over-the-counter medications ultimately make their way into water bodies and drinking-water supplies. Typical wastewater treatment plants may not be effective at removing pharmaceuticals. This is because there are no regulations limiting the release of these substances in the environment and, as a result, the needed treatment technology may not have been investigated or implemented. Knowing the best treatment practices for removing pharmaceuticals from wastewater is important for protecting drinking-water supplies as well as organisms in marine and aquatic environments because many pharmaceuticals are designed to be effective at low concentrations. A new study shows that removal of pharmaceuticals from wastewater is possible, even at very low concentrations, depending on the specific treatment process, according to researchers reporting in Environmental Science: Water Research & Technology (January 2020). See also: Environmental toxicology; Freshwater ecosystem; Marine ecology; Water pollution; Water resources; Water treatment

Microplastics are raining down on national parks and other protected areas in the western United States at the rate of about 132 pieces of microplastic per square meter every day, according to a report in the journal Science (June 2020). Microplastics are plastic particles measuring less than five millimeters (approximately 0.2 inches) in length. The reported precipitation rate is similar to dumping about 300 million pulverized plastic water bottles (about 1000 tons) over the studied areas each year. Where do these particles come from? Sources mostly include fragments from virgin plastic pellets, polymer textile fibers, microbeads from personal care products and spray paints, as well as environmental degradation of waste plastic into smaller and smaller pieces over time. See also: Manufactured fiber; Paint and coatings; Plastic waste pollution; Polymer; Textile

The benefits of outdoor physical activity (exercise) outweigh the potential harm caused by air pollution except in the most highly polluted cities, according to epidemiological studies reported in the journal Preventive Medicine (February 2016). Exercise provides a number of health benefits, including reduced risks of cardiovascular disease, type 2 diabetes, and some cancers. Cycling and walking, for example, offer not just health benefits but also environmental advantages as pollution-free means of transportation. See also: Air pollution; Cancer (medicine); Epidemiology; Heart disorders; Sports medicine; Type 2 diabetes

Although asphalt (also known as bitumen) is a naturally occurring substance found in deposits within the earth, it is also a by-product of petroleum processing. Almost all the bitumen used for asphalt pavement and roofs comes from petroleum refining and consists of hydrocarbon compounds that remain at the upper end (600°C or 1100°F) of the vacuum-distillation process. Because asphalt cannot be vacuum distilled, it has long been assumed that installed asphalt pavement and roofs do not emit hydrocarbon pollutants. Yet, according to a new report in the journal Science Advances (September 2020), asphalt pavements and roofs do, in fact, emit significant quantities of hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), particularly in environmental conditions found on hot and sunny days. This is problematic, because some PAHs are mutagens, teratogens, carcinogens, or endocrine disruptors and therefore harmful to human health and the environment. Hydrocarbons may also act as precursors to air pollutants, because hydrocarbons can react with nitrogen oxides (NO_x) and sunlight to form ozone, a major constituent of smog. See also: Air pollution; Aromatic hydrocarbon; Asphalt and asphaltite; Environmental toxicology; Nitrogen oxides; Ozone; Pavement; Petroleum; Petroleum processing and refining; Petroleum products; Roof construction; Smog

For over fifty years, heat stabilizers, light stabilizers, and antioxidants have been added to polymers to maintain their material properties by preventing their degradation. This chemical adjustment is necessary to extend the life of products such as plastic pipes, paints and coatings, and automotive parts. More recently, additives with the opposite purpose have become available: They are designed to enhance the biodegradation of hydrocarbon polymers used in common products such as plastic bags. Biodegradation is the breakdown of organic compounds by microorganisms or other biological means to their inorganic mineral constituents, such as carbon dioxide (CO₂). Biodegradation additives would seem to be an elegant solution to the mounting environmental problem of plastic waste—except that recent research indicates they do not work. See also: Antioxidant; Biodegradation; Microbial ecology; Polymer; Polyolefin resins; Stabilizer (chemistry)

Humans have used dried bovine dung (manure) as a fuel source since prehistoric times. In India, for example, many people burn cow or buffalo dung for cooking fuel. This bioresource provides a low-cost fuel as well as an efficient means of waste disposal. However, in rural India, the burning of dung is simultaneously a source of hazardous indoor and outdoor air pollution, resulting from the emission of fine particulates that are 2.5 micrometers or less in diameter (PM_2.5). Such combustion byproducts are considered the most dangerous to human health, because PM_2.5 can be inhaled deep into the lungs, impairing lung function as well as and affecting other organs, such as the heart and brain, or causing cancer. See also: Air pollution; Indoor air pollution

Neonicotinoid insecticides are the most used insecticide worldwide and have been linked to the decline of pollinator insects. In 2018, the European Union banned the outdoor use of three neonicotinoid insecticides: clothianidin, imidacloprid, and thiamethoxam. A new sulfoximine-based insecticide, called sulfoxaflor, is coming to market worldwide as a neonicotinoid replacement. Sulfoxaflor acts on the central nervous system of insects, just as neonicotinoids do, and, surprisingly (or not), it has similar harmful effects on wild bumble bees, researchers reported in Nature (August 2018). See also: Die-off of bees; Hymenoptera; Insecta; Insecticide; Neonicotinoid insecticides banned in Europe; Pesticide; Pollination

Plastic is a ubiquitous and life-saving product, but it is also rapidly becoming a significant environmental problem. Globally, less than 10 percent of plastics are recycled, about 12 percent are incinerated, and the vast majority are disposed of in landfills or littered in the natural environment. Reasons for this low rate of recycling include the low cost of feedstocks (monomers) derived from oil; inexpensive landfill space; and the fact that some plastics, such as poly(vinyl chloride), low-density polyethylene, polypropylene, and polystyrene have chemical properties that make them difficult to recycle. See also: Petroleum products; Plastic waste pollution; Polymer; Polyolefin; Polystyrene; Polyvinyl resins

During the past decade, the automotive industry has converted more than 50 percent of its internal combustion engines from a traditional technology called port fuel injection (PFI) to a new technology called gasoline direct injection (GDI). The fundamental difference between the two engine types is that GDI engines inject fuel directly into the combustion chamber instead of the injection port of the PFI engine. Benefits of GDI technology—improved fuel economy, lower carbon dioxide (CO₂) emissions, and increased power output—have resulted in rapid adoption. By 2025, the U.S. Environmental Protection Agency (EPA) projects that 93 percent of all vehicles produced will use GDI engines. However, the downside of direct fuel injection, according to a recent report in the journal Environmental Science & Technology, is a high level of black carbon (BC) aerosol emissions, which adversely affects both climate and public health. See also: Aerosol; Automobile; Carbon black; Fuel injection; Gasoline; Internal combustion engine

Since 1975, approximately 1200 dams have been removed from rivers in the United States, including 72 in 2014. Some of these dams were in danger of failure, others had become functionally obsolete because their reservoirs had filled with sediment, and a few were removed to restore the rivers’ ecosystems. Originally, these dams were built for water storage, hydropower, irrigation, navigation, and flood control; however, most were built with little regard for the environmental consequences. See also: Dam; Ecosystem; Fluvial sediments; Reservoir; River