David Kitchen, University of Richmond Volcanoes inspire awe with spectacular eruptions and incandescent rivers of lava, but often their deadliest hazard is what quietly falls from the sky. When a large volcano erupts, as Mount Spurr appears close to doing about 80 miles from Anchorage, Alaska, it can release enormous volumes of ash. Fine ash can infiltrate the lungs of people and animals who breathe it in, poison crops and disrupt aquatic life. Thick deposits of ash can collapse roofs, cripple utilities and disrupt transport networks. Ash may lack the visual impact of flowing lava, but as a geologist who studies disasters, I’m aware that ash travels farther, lasts longer and leaves deep scars.

Volcanic ash: What it is, and why it matters

Volcanic ash forms when viscous magma – molten rock from deep beneath Earth’s surface – erupts, exploding into shards of rock, mineral and glass carried in a near-supersonic stream of hot gas. Towering clouds of ash rise several miles into the atmosphere, where the ash is captured by high-altitude winds that can carry it hundreds or even thousands of miles. As the volcanic ash settles back to Earth, it accumulates in layers that typically decrease in thickness with distance from the eruption source. Near the vent, the ash may be several feet deep, but communities farther away may see only a dusting.

Breathing danger: Health risks from ash

Breathing volcanic ash can irritate the throat and lungs, trigger asthma attacks and aggravate chronic respiratory conditions such as COPD. The finest particles pose the greatest risk because they can penetrate deep into the lungs and cause death by asphyxiation in the worst cases. Mild, short-term symptoms often resolve with rest. However, the long-term consequences of ash exposure can include silicosis, a lung disease and a possible cause of cancer. The danger increases in dry regions where fallen ash can be kicked up into the air again by wind or human activity.

Risks to pets and livestock

Humans aren’t the only ones at risk. Animals experience similar respiratory symptoms to humans. Domestic pets can develop respiratory distress, eye inflammation and paw irritation from exposure to ash.

Livestock face greater dangers. If grazing animals eat volcanic ash, it can damage their teeth, block their intestines and poison them. During the 2010 Eyjafjallajökull eruption in Iceland, farmers were advised to shelter sheep and cattle because the ash contained fluoride concentrations above the recognized safety threshold of 400 parts per million. Animals that remained exposed became sick and some died.

Harm to crops, soil and water

Soil and crops can also be damaged. Volcanic ash alters the acidity of soil and introduces harmful elements such as arsenic and sulfur into the environment. While the ash can add nutrients such as potassium and phosphorus that enhance fertility, the immediate impact is mostly harmful. Ash can smother crops, block sunlight and clog the tiny stomata, or pores, in leaves that allow plants to exchange gases with the atmosphere. It can also introduce toxins that render food unmarketable. Vegetables, fruit trees and vines are particularly vulnerable, but even sturdy cereals and grasses can die if ash remains on leaves or poisons emerging shoots. Following the 1991 Mount Pinatubo eruption, vast tracts of farmland in central Luzon in the Philippines were rendered unproductive for years due to acidic ash and buried topsoil. If multiple ashfalls occur in a growing season, crop failure becomes a near certainty. It was the cause of a historic famine that followed the eruption of Mount Tambora in 1815.

Ash can also contaminate surface water by introducing toxins and increasing the water’s acidity. The toxins can leach into groundwater, contaminating wells. Fine ash particles can also settle in waterways and smother aquatic plants and animals. During the 2008 Chaitén eruption in Chile, ash contamination led to widespread fish deaths in the Río Blanco.

Ash can ground airplanes, gum up infrastructure

Ash clouds are extremely dangerous to aircraft. The glassy ash particles melt when sucked into jet turbines, clog fuel systems and can stall engines in midair. In 1982, British Airways Flight 9 lost power in all four engines after flying through an ash cloud. A similar incident occurred in 1989 to KLM Flight 867 over Alaska. In 2010, Iceland’s Eyjafjallajökull eruption grounded more than 100,000 flights across Europe, disrupting travel for over 10 million passengers and costing the global economy billions of dollars. Volcanic ash can also wreak havoc on infrastructure by clogging water supplies, short-circuiting electrical systems and collapsing roofs under its weight. It can disrupt transportation, communication, rescue and power networks, as the 1991 eruption of Mount Pinatubo in the Philippines dramatically demonstrated.

What to do during ashfall

During an ashfall event, the most effective strategy to stay safe is to stay indoors as much as possible and avoid inhaling ash particles. Anyone who must go outside should wear a properly fitted N95 or P2 mask. Cloth masks provide little protection against fine ash. Rainwater tanks, troughs and open wells should be covered and monitored for contamination. Livestock should be moved to clean pastures or given uncontaminated fodder.

To reduce structural damage, ash should be cleared from roofs and gutters promptly, especially before rainfall. Older adults, children and people who are sick are at greatest risk, particularly those living in poorly ventilated homes. Rural communities that are dependent on agriculture and livestock are disproportionately affected by ashfall, as are low-income people who lack access to clean water, protective masks or safe shelter. Communities can stay informed about ash risks through official alerts, including those from the Volcanic Ash Advisory Centers, which monitor ash dispersion and issue timely warnings. The International Volcanic Health Hazard Network also offers guidelines on personal protection, emergency planning and ash cleanup.

The long tail of ash

Volcanic ash may fall quietly, but its effects are widespread, persistent and potentially deadly. It poses a chronic threat to health, agriculture, infrastructure and aquatic systems. Recognizing the risk is a crucial first step to protecting lives. Effective planning and public awareness can further help reduce the damage. David Kitchen, Associate Professor of Geology, University of Richmond This article is republished from The Conversation under a Creative Commons license. Read the original article.

Ron Barrett, Macalester College Disease forecasts are like weather forecasts: We cannot predict the finer details of a particular outbreak or a particular storm, but we can often identify when these threats are emerging and prepare accordingly. The viruses that cause avian influenza are potential threats to global health. Recent animal outbreaks from a subtype called H5N1 have been especially troubling to scientists. Although human infections from H5N1 have been relatively rare, there have been a little more than 900 known cases globally since 2003 – nearly 50% of these cases have been fatal – a mortality rate about 20 times higher than that of the 1918 flu pandemic. If the worst of these rare infections ever became common among people, the results could be devastating. Approaching potential disease threats from an anthropological perspective, my colleagues and I recently published a book called “Emerging Infections: Three Epidemiological Transitions from Prehistory to the Present” to examine the ways human behaviors have shaped the evolution of infectious diseases, beginning with their first major emergence in the Neolithic period and continuing for 10,000 years to the present day. Viewed from this deep time perspective, it becomes evident that H5N1 is displaying a common pattern of stepwise invasion from animal to human populations. Like many emerging viruses, H5N1 is making incremental evolutionary changes that could allow it to transmit between people. The periods between these evolutionary steps present opportunities to slow this process and possibly avert a global disaster.

Spillover and viral chatter

When a disease-causing pathogen such as a flu virus is already adapted to infect a particular animal species, it may eventually evolve the ability to infect a new species, such as humans, through a process called spillover. Spillover is a tricky enterprise. To be successful, the pathogen must have the right set of molecular “keys” compatible with the host’s molecular “locks” so it can break in and out of host cells and hijack their replication machinery. Because these locks often vary between species, the pathogen may have to try many different keys before it can infect an entirely new host species. For instance, the keys a virus successfully uses to infect chickens and ducks may not work on cattle and humans. And because new keys can be made only through random mutation, the odds of obtaining all the right ones are very slim. Given these evolutionary challenges, it is not surprising that pathogens often get stuck partway into the spillover process. A new variant of the pathogen might be transmissible from an animal only to a person who is either more susceptible due to preexisting illness or more likely to be infected because of extended exposure to the pathogen. Even then, the pathogen might not be able to break out of its human host and transmit to another person. This is the current situation with H5N1. For the past year, there have been many animal outbreaks in a variety of wild and domestic animals, especially among birds and cattle. But there have also been a small number of human cases, most of which have occurred among poultry and dairy workers who worked closely with large numbers of infected animals.

Epidemiologists call this situation viral chatter: when human infections occur only in small, sporadic outbreaks that appear like the chattering signals of coded radio communications – tiny bursts of unclear information that may add up to a very ominous message. In the case of viral chatter, the message would be a human pandemic. Sporadic, individual cases of H5N1 among people suggest that human-to-human transmission may likely occur at some point. But even so, no one knows how long or how many steps it would take for this to happen. Influenza viruses evolve rapidly. This is partly because two or more flu varieties can infect the same host simultaneously, allowing them to reshuffle their genetic material with one another to produce entirely new varieties.

These reshuffling events are more likely to occur when there is a diverse range of host species. So it is particularly concerning that H5N1 is known to have infected at least 450 different animal species. It may not be long before the viral chatter gives way to larger human epidemics.

Reshaping the trajectory

The good news is that people can take basic measures to slow down the evolution of H5N1 and potentially reduce the lethality of avian influenza should it ever become a common human infection. But governments and businesses will need to act. People can start by taking better care of food animals. The total weight of the world’s poultry is greater than all wild bird species combined. So it is not surprising that the geography of most H5N1 outbreaks track more closely with large-scale housing and international transfers of live poultry than with the nesting and migration patterns of wild aquatic birds. Reducing these agricultural practices could help curb the evolution and spread of H5N1.

People can also take better care of themselves. At the individual level, most people can vaccinate against the common, seasonal influenza viruses that circulate every year. At first glance this practice may not seem connected to the emergence of avian influenza. But in addition to preventing seasonal illness, vaccination against common human varieties of the virus will reduce the odds of it mixing with avian varieties and giving them the traits they need for human-to-human transmission. At the population level, societies can work together to improve nutrition and sanitation in the world’s poorest populations. History has shown that better nutrition increases overall resistance to new infections, and better sanitation reduces how much and how often people are exposed to new pathogens. And in today’s interconnected world, the disease problems of any society will eventually spread to every society. For more than 10,000 years, human behaviors have shaped the evolutionary trajectories of infectious diseases. Knowing this, people can reshape these trajectories for the better. Ron Barrett, Professor of Anthropology, Macalester College This article is republished from The Conversation under a Creative Commons license. Read the original article.