Society for the Advancement of Animal Wellbeing

- Protecting Animals and Conserving the Environment

Animal Agriculture, the Environment and Human Health

In this section we will be looking at the indirect effects of the meat industry on human health. The direct effect of eating meat are well known and include heart disease, viruses like avian flu, bacteria for example E.coli and salmonella as well as prion proteins like mad cow disease.

However animal agriculture has various negative impacts on the environment and subsequently on human health, this is important because even if you don’t eat meat you could be inadvertently affected by the industry’s environmental impact. As meat production has become more industrialized, factory farms have become more common. These operations usually have thousands or tens of thousands of animals in close confinement at any one time. The results of such farming methods have implications for the surrounding area as well as globally.


Dust storms


It is estimated that at any one time there are 3.2 billion livestock animals on the planet that’s not including poultry or pigs. To feed these animals requires huge amounts of grain predominantly soya bean. In order to grow the food for the livestock, vast amounts of rainforest are cut down to be turned in to agricultural land. 70 to 80 % of all agricultural land is used by the meat industry to feed animals, that’s 30% of the world’s total land mass.

So what are the health effects of such excessive deforestation. At first the forest land’s nutrient rich top soil is washed away by the rain, with no trees the land can no longer hold the water or soil. After sometime, the rains brought in by the natural humidity of the forest stop falling, the land thus becomes arid and dry through the process known as desertification.


Desertification can affect people’s health even if they are living in an entirely different continent. A UN report, the Millennium Ecosystem Assessment, which relied on 1,300 experts from 95 countries, stated that “an increase in desertification-related dust storms is widely considered to be a cause of ill-health (fever, coughing, sore eyes) during the dry season.

Dust emanating from the Gobi desert and the Sahara has also been implicated in respiratory problems as far away as North America and has affected coral reefs in the Caribbean.” Evidence also shows that that the dust storms originating from the Gobi desert also affect the air quality and lung health in China, Korea and Japan.

Currently 41% of the world’s land area is dry or arid and is therefore negatively impacting the lives of the estimated 2 billion people that live in around such areas. European World Health Organization (WHO) regional Director Dr. Roberto Bertollini said “As environmental changes increasingly impinge on human health on an unprecedented and global scale, we are becoming increasingly concerned with the consequences of desertification and drought, such as malnutrition and famine, waterborne diseases, other infectious diseases, respiratory diseases and burn injuries. Although further research is necessary, there is sufficient evidence that desertification and drought harm human health."

Other effects

 Rising food prices, malnutrition due to lack of nutrient rich soil as well as drought are all a result of the meat industry’s need for cheap fodder to feed livestock animals.

The WHO pointed out that the lack of water in these regions forces people to drink from un-clean water sources thus causing outbreaks of various diseases including cholera, typhoid, hepatitis A and gastro-enteric diseases.  The lack of resources also causes regional instability and conflict when people start competing for scarce food and water.

Dr Bettina Menne of WHO's global change and health program said "In Africa, some 49% of the 10 million annual deaths among children under 5 years of age are associated with malnutrition. Desertification, deforestation and overuse of wilderness areas have drastically reduced the amount of supplementary products gathered in the bush, which provide nutritional supplements to entire families.

Furthermore, changes in local biodiversity can put at risk traditional medicine, which plays a very important role all over Africa."

Water Pollution

The main source of pollution from the meat industry is the fecal matter both solid and liquid that is produced. To most it may not sound like a big issue but the huge amounts produced on a daily basis has very serious consequences for the environment and human health. The average Holstein dairy cow produces over 115 pounds of manure a day that is approximately 21 tons per year.

In the US it estimated that 2 trillion pounds of animal waste is produced per annually. According to Mr. Wu Weixiang associate professor with the Department of Environment Engineering at Zhejiang University in China, livestock produces 2.7 billion tons of waste per year and has become one of the largest pollution sources in the country.


So how does this affect human health?


There are a variety of methods for the management of waste, usually it is mixed with water to form slurry, this slurry is then stored in large open lagoons, some several acres in size. Although the lagoons are coated with either cement or plastic, these protective layers often crack and cause the slurry to leak in to the ground.

The manure is also sprayed on to certain crops as a fertilizer due to its high nitrogen content Often this spraying causes the manure to seep in to the ground water and often drains in to lakes and streams. So, leakage from lagoons and seeping nitrates from manure fertilizers enter our water systems. These nitrates have a serious adverse effect on human health and particularly on infant health.

Increased nitrate and nitrite levels of drinking water have been associated with an increase in spontaneous abortions as reported by the Center for Disease Control as well as blue baby syndrome. Blue baby syndrome also known as methemoglobinemia is caused when ingestion of nitrates cause the blood to become depleted of oxygen. It can be fatal but is easily treated once diagnosed.

In adults, studies by scientists Wolfe and Patz of the John Hopkins School of Public Health revealed that long term consumption of nitrates can lead to stomach, ovarian, liver and central nervous system cancers or tumors. Not only do the nitrates leach in to the water but they also get in to the atmosphere.

As manures decomposes the bacterial anaerobic process produces nitrogen based gases as well as hundreds of other noxious gases including ammonia and methane. The detrimental health effects from these gases are varied and it has been shown that ammonia can cause asthma. Nitrogen oxide gases also reacts with other chemicals to form O3 compounds which cause respiratory tract infection as well as reduced lung function. Nitrogen oxides can also worsen common viral infections and aggravate asthmatic conditions. Some studies show that children who are raised in elevated nitrogen oxide or ozone compound areas have a 40% increased chance of developing asthmatic conditions.

As these industrialized farms set up closer to urban areas with large population the effects of the meat industry on human health becomes more evident and poses a greater risk. These effects however are not localized as wind can carry contaminants over large areas and water supplies as well as water ways travel over long distances.

Another by product from the meat industry is hydrogen sulfide (H2S). There are 2 main sources of this extremely noxious gas. The first is directly from anaerobic decomposition of manure, predominantly from pig waste.

Hydrogen sulfide is by far the most dangerous gas of all those produced from manure; even at low concentrations it can cause sore throats, seizures and comas. Continued exposure to hydrogen sulfide can cause loss of life and such incidents do occur on a yearly basis at swine waste processing plants.

Studies measuring the air quality at livestock facilities showed that hydrogen sulfide exposure was also associated with increased occurrence of headaches and respiratory tract infection, there were also adverse effects on unborn fetuses.


Algal Blooms


The second source of hydrogen sulfide as well as other dangerous gases is from the eutrophication of lakes and other bodies of water. Eutrophication is also known as algal bloom. The fertilizer run of from farms as well as leakage from manure lagoons finds its way into the ground water as well as the rivers and lakes.

The nitrogen in the fertilizers causes a massive spurt of growth in the amount various algae or phytoplankton, this causes the amount of oxygen in the water to decrease and hence the marine suffer and die. As the organic matter from the marine animals decomposes this further reduces the oxygen levels of the water creating large areas of water with no life known as dead zones.

In such extreme anaerobic conditions ocean bacteria will use sulfur as an energy source, this chemical process produces hydrogen sulfide as a waste product. This problem is further amplified by the rising temperatures of the seas due to global warming, as warmer water hold less oxygen thus leading to increased hydrogen sulfide production. It is actually this very process of that is blamed for one of the great extinctions that occurred 250 million years ago during the Permian period.



The harmful algal blooms caused by manure pollution from the meat industry vary in their effects on the environment. For example in Florida in the Gulf of Mexico blooms of a marine dinoflagellate have been known to turn the water red just by the huge amount of the organism present in the water, this is commonly known as red tide and is caused by the phytoplankton species K. brevis.  The plankton produce a potent poison called brevotoxin.

Due to wave and wind action these toxins can be aerosolized and carried in to the air. Experiments conducted by the National Center for Environmental Health showed that brevotoxins are powerful bronchoconstrictors and can cause respiratory symptoms to those exposed, this would be particularly harmful for those suffering from asthma, potentially triggering an attack.


 Pathogen contamination of Water Sources

Contamination of ground water with a variety of pathogens is also quite a common source of disease for humans. Manure and waste contains many microbes, bacteria and viruses, all of which can make us sick if they find a way in to our water.

There are many such microbes a lot of which are water borne and infectious even at low concentration. Some like E.coli may remain viable for up to 260 days in a water reservoir, some are even resistant to treatment as they have become resistant to antibiotics. The most common and life threatening form of contamination is from E.coli 0157:H7. This form of E.coli can be fatal as it causes kidney failure in the host. In one such outbreak that occurred in Walkerton, Canada 2,300 individual had gastroenteritis, 65 people were hospitalized, 27 developed long term kidney conditions and there were 7 mortalities.

Apart from the staggering human cost the financial cost was also significant at US$155 million. The outbreak was caused by E.coli and Campylobacter. Evidence suggests that the cause was manure run-off from a nearby farm that had entered the water system. Indeed a study from the Center of Disease control shows that an increase in the cattle population per hectare also causes a subsequent increase in the number of infections. Outbreaks such as these are not a rare event just in British Columbia alone there have been 29 such events since 1980.


The toll the meat industry has on human health is substantial, even if you do not consume their product. The unnatural conditions, the massive number of animals and the management methods all lead to an industry that is making the environment sick. But by the far the most damaging effect of the meat industry on the environment and subsequently on human health is its carbon intensity. The deforestation as well as the transport of animals and the meat products means the meat industry is responsible for 18% of total greenhouse gas emissions that is 4% more than all transport vehicles and cars. The cost on human health is incalculable, rising sea levels climate changes affect everyone and every animal on this planet, no one can escape the livestock’s long shadow. To save our own health and the health of the planet, changing to a healthy vegan or vegetarian diet is the simplest and most effective way. To find out how, please visit our go veg page.


 Return to the main page of the Environmental section.

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