Concepts of Environmental Health 1
PUH 5305, Concepts of Environmental Health 1
Course Learning Outcomes for Unit II Upon completion of this unit, students should be able to:
1. Discuss the effects of major environmental and occupational agents. 1.1 Explain how zoonotic diseases are transferred to humans. 1.2 Discuss the history and etiology of a vector-borne disease.
2. Summarize the factors that affect susceptibility to adverse health outcomes following exposure to
environmental hazards. 2.1 Discuss how toxic metals affect the human population in the environment.
Course/Unit Learning Outcomes
Learning Activity
1.1 Unit Lesson Chapter 5 Unit II Assessment
1.2 Unit Lesson Chapter 5 Unit II Assessment
2.1 Unit Lesson Chapter 6 Unit II Assessment
Required Unit Resources Chapter 5: Zoonotic and Vector-Borne Diseases Chapter 6: Toxic Metals and Elements
Unit Lesson Introduction Zoonoses or zoonotic diseases are caused by contagions that spread between people and animals. Thousands of Americans every year get sick from infectious diseases that are spread from animals to people or from heavy metals to people from materials such as mercury, nickel, and lead and other compounds like tin, aluminum, and iron. The Centers for Disease Control and Prevention (CDC) has been working diligently in tracking these diseases and looking for ways to assist the public and environmental health specialists in eradicating or reducing the occurrence of these diseases (CDC, 2017b). Vector-borne diseases are the diseases that can be transmitted from animals (vector) to humans. Vector was often restricted to arthropods, such as mosquitoes and ticks, but it is generally used for animals that could transmit pathogens to human hosts (CDC, 2017a). Vector-borne diseases are usually also referred to as zoonotic diseases that originate from animals even though some of these diseases, such as malaria and yellow fever, could be transmitted from human to human. Heavy metals, on the other hand, are widely distributed in the environment and come from both man-made and natural sources (Tchounwou et al., 2012). The human population is generally exposed to some levels of heavy metals from natural components on earth, but other sources of exposure are linked to emissions from
UNIT II STUDY GUIDE
Environmental Agents, Part I
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coal and power plants, digestion of contaminated water and food, contact with occupation-related metals, and contact with leaching contaminants from perilous waste sites. Vector-borne Diseases and Zoonoses There are many diseases that fall into this category. Your textbook examines some of these, and we will look at a few in more detail in this lesson.
Examples of Vector-borne Diseases and Zoonoses
Bacterial Anthrax, tularemia, Cat-scratch disease, E. coli infection, Lyme disease, psittacosis, salmonellosis, and plague
Viral Zika virus, West Nile virus, dengue fever, encephalitis, hantavirus, monkeypox, influenza, avian influenza, swine flu, yellow fever, rabies, Rift Valley fever, and foot and mouth disease
Parasitic Malaria, giardiasis, cryptosporidiosis, cysticercosis and taeniasis, leishmaniasis, and trichinellosis
Rickettsial Q fever and Rocky Mountain Spotted Fever
Nonconventional Mad Cow Disease and Variant Creutzfeldt-Jakob disease
Zika virus: Zika virus is as a result of the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus). The mosquitoes bite at night and during the day. The Zika virus can be transferred from a pregnant woman to her fetus and this infection can cause birth defects (CDC, 2019e; Rasmussen et al., 2016). The Zika virus can also be passed during sexual intercourse, so infected people should practice safe sex or simply avoid sexual intercourse. The safest way to avoid being infected by the Zika virus is to avoid being bitten by the mosquito because there is no vaccine for the Zika virus (CDC, 2019e). The Zika virus infection generally does not have any symptoms except for a mild, self-limiting malaise, but it has been linked to quite a number of serious neurological diseases with the most common being the Guillain- Barré syndrome and congenital microcephaly syndrome (Song et al., 2017).
The Zika virus was originally discovered in Uganda around 1947, and from about 1960 to about 1980, infected humans were found throughout Asia and Africa (Kindhauser et al., 2016). The largest outbreak was reported in 2007 on the island of Yap of the Federated States of Micronesia. There was another outbreak in 2013 to 2014 in French Polynesia (Kindhauser et al., 2016). Zika spread eastward from equatorial Africa and Asia to the Pacific Islands during the late 2000s to early 2010s, invaded the Caribbean and Central and South America in 2015, and reached North America in 2016. No mosquito transmission of the virus was reported in the United States in 2018 and but in 2015 and 2016, large Zika virus outbreaks were reported in the United States from travelers who visited the mosquito-infested areas as well as a few cases in Texas and Florida (CDC, 2019e).
There was also an extensive transmission rate in the Virgin Islands and Puerto Rico, but by 2017, the number of occurrences had declined (CDC, 2019e). Anthrax: Anthrax is a deadly infectious disease caused by rod-shaped, gram-positive bacteria and is a germ that lives in the soil called bacillus anthracis (Goel, 2015). It is rare, however, that humans would get sick if they come into contact with contaminated animal products or infected animals. The animals that are most affected are goats, cattle, and sheep. Anthrax could be contracted from infected hides, animals, meat, and
The Zika virus can be transmitted by mosquitos. (Trueffelpix, n.d.)
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wool. Anthrax causes three forms of diseases in humans (Banerjee et al., 2017). Those diseases include the following:
• cutaneous (affects the skin): open sores or cuts could get infected after coming in contact with the bacteria,
• inhalation (affects the lungs): breathing the spores of the bacteria, and
• gastrointestinal (affects the digestive system): eating meat that is infected. Cutaneous anthrax is the most common among human beings and accounts for at least 95% of all reported cases (Banerjee et al., 2017; Vieira et al., 2017). Signs and symptoms of anthrax would depend on how the human was infected, but they range from shock to skin sores, to vomiting. Immediate treatment with antibiotics is needed to cure this disease but the inhaled anthrax is the most difficult to treat and could be fatal (Mayo Clinic, n.d). There is currently a vaccine for anthrax for those in the military and for those that are at a high risk of being exposed. Quite a few people are aware of anthrax following the bioterror attacks of 2001 (Goel, 2015). Anthrax was sent by mail to a few people, killing five and making 22 others very sick. The most recent case in the United States was in 2011, when a retired Florida man, Dan Anders, and his wife, Anne, went on a three-week, cross-country trip through Wyoming, Montana, North Dakota, and South Dakota (Griffith et al., 2014). After three weeks in the hospital and an investigation by the FBI and CDC, it was concluded that there were no bioterrorism threats and Mr. Anders had suffered from a rare but natural case of inhalation of anthrax. He fully recovered. Malaria: Malaria is a mosquito-borne and acute febrile illness caused by a parasite called the female Anopheles mosquito (CDC, 2019b).
Symptoms of malaria are similar to the flu, including chills and fever. If left untreated, malaria could be deadly. The initial symptoms (chills, fever, and headache) are usually mild and difficult to recognize because they may feel like the flu or a cold. After 24 hours, it may slowly progress to acute malaria with symptoms such as cerebral malaria, anemia, organ failure, and, subsequently, death (World Health Organization [WHO], 2019).
The life cycle of malaria (CDC, 2019b)
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In malaria endemic regions, however, some people, especially healthy adults, have developed a type of immunity, which has allowed them to be asymptomatic. Malaria is one of the leading causes of death in sub-Saharan Africa (Nkoka et al., 2019). More than 219 million people worldwide were diagnosed with malaria in 2017 while an estimated 435,000 died of the disease, the majority of whom being children in the African region (CDC, 2019b). In the United States, it was reported that about 1,700 malaria cases were diagnosed, and the vast majority were immigrants or travelers who returned from South Asia and sub-Saharan Africa (CDC, 2019b). Q Fever: Q fever is a disease that is caused by bacteria Coxiella burnetii. It naturally infects some animals, such as cattle, goats, and sheep (CDC, 2019d). Coxiella burnetii bacteria are found in the milk of infected animals, urine, feces, and birth products (amniotic fluid or the placenta). Humans are usually infected by contaminated dust from infected milk, urine, birth products, and animal feces (CDC, 2019d). While some people might never become sick, others may experience symptoms such as muscle pain, fatigue, fever, and chills. Q fever was initially discovered in humans in 1935 in Australia, and in in the 1940s in the United States. It subsequently became a notifiable disease in 1999 (CDC, 2019c). In 2000, 19 cases of Q fever were reported in the United States, and in 2007, that number increased to 173 (CDC, 2019c). Between 2008 and 2013, the numbers decreased. In 2017, 153 cases were reported. Toxic Metals in the Environment and the Effect on People Heavy metals are metallic elements that are relatively high density when compared to water (Tchounwo et al., 2012). Assuming that toxicity and heaviness are interrelated, heavy metals could include arsenic metalloids that induce low-level toxicity exposure. Public health officials have increasingly been worried about the environment being contaminated by metals as human exposure has dramatically increased from many technological, domestic, agricultural, and industrial applications (Tchounwo et al., 2012). Heavy metals in the environment include industrial, domestic effluents, geogenic, atmospheric, pharmaceutical, and agricultural sources. Environmental pollution, for example, is extremely common because of smelters, mining, and foundries (Tchounwo et al., 2012). While some metals are essential nutrients for physiological and several biochemical functions (magnesium, iron, copper, cobalt, zinc, molybdenum, nickel, and manganese), inadequate supply of these nutrients could lead to deficiency syndromes and diseases. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in alliance with the amended Superfund Amendments and Reauthorization Act (SARA), requires the Agency for Toxic Substances and Disease Registry (ATSDR) and the U.S. Environmental Protection Agency (EPA) to prepare a priority order list of substances that are most common in the National Priorities List (NPL) facilities. These metals have been determined to be a significant threat to human health because of their suspected harmfulness and possible human exposure at these NPL sites (ATSDR, 2017). ATSDR lists arsenic, lead, mercury, vinyl chloride, and polychlorinated biphenyls as the top five causes of poisoning among humans and the environment. Arsenic: Arsenic is a natural substance that is highly present and toxic in its inorganic form in the groundwater of several countries (Minatel et al., 2018). Humans could be exposed through irrigation of food crops, food preparations, and drinking water. However, in low levels, arsenic could also be found in dairy products, cereals, poultry, shellfish, meat, and fish. Smokers are also exposed to arsenic through the natural inorganic content of tobacco because the plants take up the natural content of arsenic in the soil (Mandal, 2017). Long-term exposure to arsenic causes cancer and skin lesions as well as diabetes and cardiovascular diseases (Minatel et al., 2018). Exposure during pregnancy and early childhood have also resulted in increased deaths and cognitive development among children and young adults. The most significant action in affected populations is preventing further exposure to arsenic by providing safe water supplies for communities (WHO, 2018a).
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Public health officials have particularly faced threats of high levels of contaminated water in several countries, including the United States, Bangladesh, Mexico, Argentina, India, China, and Chile (Mandal, 2017). Lead: Lead is considered one of the most hazardous and increasing environmental contaminants that affect all biological organisms through exposure to food, air, and water (WHO, 2018b). It is particularly harmful to children, who are exposed by living in old houses or through toys. Lead is circulated in all parts of the environment in three main systems (Assi et al., 2016):
• organic lead containing carbon,
• metallic lead, and
• lead salts. This cumulative toxicant is distributed to the bones, kidney, liver, and brain. It is stored in the bones and teeth, where it accrues over a period of time at which the level can be assessed through a blood test (WHO, 2018b). It is also extremely dangerous to pregnant women because it can be passed through the bloodstream of the mother to the fetus. No amount of lead exposure is considered safe, and exposure to lead is also preventable (WHO, 2018b). Exposure to lead over time may lead to nausea, irritability, abdominal pain, distraction, forgetfulness, constipation, and depression (National Institute for Occupational Safety and Health [NIOSH], 2018). Prolonged exposure could also lead to reduced fertility, heart disease, high blood pressure, and kidney disease.
Normally, lead mostly affects children as opposed to adults. Children may show signs of severe lead poisoning at lower levels than adults. It usually also occurs in children whose parents unintentionally bring home lead dust from work on their clothes. Mental retardation and neurological effects have reportedly been common among children whose parents may have work-related lead exposure (NIOSH, 2018). The main sources of work-related lead exposure are batteries, leaded gasoline, and lead-based paints (Assi et al., 2016). Public health officials are especially concerned with lead as it is most dangerous to children. The CDC, for example, created a program in agreement with the Healthy People 2020 goals (the Childhood Lead Poisoning Prevention Program) that is committed to eliminating lead blood levels and the average risk from a social and racial perspective in the community (CDC, 2019a).
The effects of lead on children. (National Center for Environmental Health, n.d.)
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Conclusion The examples listed in this unit provide a synopsis of how the environment and humans could be affected when exposed to hazardous elements. According to the Healthy People 2020 goals, poor environmental quality greatly affects those whose health is most vulnerable, especially children.
References Agency for Toxic Substances and Disease Registry. (2017). ATSDR’s substance priority list. Centers for
Disease Control and Prevention. https://www.atsdr.cdc.gov/spl/ Assi, M. A., Hezmee, M. N. M., Haron, A. W., Sabri, M. Y. M., & Rajion, M. A. (2016). The detrimental effects
of lead on human and animal health. Veterinary World, 9(6), 660–671. http://www.veterinaryworld.org/Vol.9/June-2016/20.html
Banerjee, D., Chakraborty, B., & Chakraborty, B. (2017, September/October). Anthrax: Where margins are
merging between emerging threats and bioterrorism. Indian Journal of Dermatology, 62(5), 456–458. https://doi.org/10.4103/ijd.IJD_378_17
Centers for Disease Control and Prevention. (2017a). Anthrax. https://www.cdc.gov/anthrax/index.html Centers for Disease Control and Prevention. (2017b). Zoonotic diseases.
https://www.cdc.gov/onehealth/basics/zoonotic-diseases.html Centers for Disease Control and Prevention. (2019a). Childhood lead poisoning prevention.
https://www.cdc.gov/nceh/lead/default.htm Centers for Disease Control and Prevention. (2019b). Malaria.
https://www.cdc.gov/parasites/malaria/index.html Centers for Disease Control and Prevention. (2019c). Q fever. https://www.cdc.gov/qfever/index.html Centers for Disease Control and Prevention. (2019d). Q fever: Epidemiology and statistics.
https://www.cdc.gov/qfever/stats/index.html Centers for Disease Control and Prevention. (2019e). Questions about Zika.
https://www.cdc.gov/zika/about/questions.html Goel, A. K. (2015, January 16). Anthrax: A disease of biowarfare and public health importance. World Journal
of Clinical Cases, 3(1), 20–33. https://doi.org/10.12998/wjcc.v3.i1.20 Griffith, J., Blaney, D., Shadomy, S., Lehman, M., Pesik, N., Tostenson, S., Delaney, L., Tiller, R., DeVries,
A., Gomez, T., Sullivan, M., Blackmore, C., Stanek, D., Lynfield, R., & Anthrax Investigation Team. (2014, February). Investigation of inhalation anthrax case, United States. Emerging Infectious Diseases, 20(2), 280–283. https://doi.org/10.3201/eid2002.130021
Kindhauser, M. K., Allen, T., Frank, V., Santhana, R. S., & Dye, C. (2016). Zika: The origin and spread of a
mosquito-borne virus. Bulletin of the World Health Organization, 94(9), 675–686C. https://doi.org/10.2471/BLT.16.171082
Mandal, P. (2017, March). An insight of environmental contamination of arsenic on animal health. Emerging
Contaminants, 3(1), 17–22. Mayo Clinic. (n.d.). Anthrax. Symptoms and causes. https://www.mayoclinic.org/diseases-
conditions/anthrax/symptoms-causes/syc-20356203
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Minatel, B. C., Sage, A. P., Anderson, C., Hubaux, R., Marshall, E. A., Lam, W. L., & Martinez, V. D. (2018, March). Environmental arsenic exposure: From genetic susceptibility to pathogenesis. Environment International, 112, 183–197.
National Center for Environmental Health. (n.d.). Prevent children’s exposure to lead. Centers for Disease
Control and Prevention. https://www.cdc.gov/features/leadpoisoning/index.html National Institute for Occupational Safety and Health. (2018). Health problems caused by lead. Centers for
Disease Control and Prevention. https://www.cdc.gov/niosh/topics/lead/health.html Nkoka, O., Chipeta, M. S., Chuang, Y.-C., Fergus, D., & Chuang, K.-Y. (2019). A comparative study of the
prevalence of and factors associated with insecticide-treated nets usage among children under 5 years of age in households that already own nets in Malawi. Malaria Journal, 18(1), Article 43. https://doi.org/10.1186/s12936-019-2667-4
Rasmussen, S. A., Jamieson, D. J., Honein, M. A., & Petersen, L. R. (2016, May 19). Zika virus and birth
defects—reviewing the evidence for causality. New England Journal of Medicine, 374(20), 1981– 1987. https://doi.org/10.1056/NEJMsr1604338
Song, B.-H., Yun, S.-I., Woolley, M., & Lee, Y.-M. (2017, July 15). Zika virus: History, epidemiology,
transmission, and clinical presentation. Journal of Neuroimmunology, 308, 50–64. https://doi.org/10.1016/j.jneuroim.2017.03.001
Tchounwou, P. B., Yedjou, C. G., Patlolla, A. K., & Sutton, D. J. (2012). Heavy metal toxicity and the
environment. Experientia Supplementum, 101, 133–164. https://doi.org/10.1007/978-3-7643-8340- 4_6
Trueffelpix. (n.d.). ID 66209432 [Image]. Dreamstime. https://www.dreamstime.com/stock-photo-zika-virus-
illustration-symbol-attention-image66209432 Vieira, A. R., Salzer, J. S., Traxler, R. M., Hendricks, K. A., Kadzik, M. E., Marston, C. K., Kolton, C. B.,
Stoddards, R. A., Hoffmaster, A. R., Bower, W. A., & Walke, H. (2017). Enhancing surveillance and diagnostics in anthrax-endemic countries. Emerging Infectious Diseases, 23(13), S147–S153. https://doi.org/10.3201/eid2313.170431
World Health Organization. (2018a, February 15). Arsenic. https://www.who.int/news-room/fact-
sheets/detail/arsenic World Health Organization. (2018b). Lead poisoning and health. https://www.who.int/news-room/fact-
sheets/detail/lead-poisoning-and-health World Health Organization. (2019). Malaria. https://www.who.int/news-room/fact-sheets/detail/malaria
Suggested Unit Resources In order to access the following resources, click the links below. The film clip below will give you more information about one disease covered in this lesson: anthrax. Nevco Educational Video Inc. (Producer). (2004). Anthrax (Segment 2of 9) [Video]. In Bio-Terrorism:
Information for the Health Care Professional. Films on Demand. https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=http://fod.infobase.com/PortalPla ylists.aspx?wID=273866&xtid=43847&loid=125269
The transcript for this video can be found by clicking on “Transcript” in the gray bar at the top of the video in the Films on Demand database.
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The article below further explores the issue of lead poisoning. Rosner, D. (2014). Imagination and public health: The end of lead poisoning in California? The Milbank
Quarterly, 92(3), 430–433. https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc t=true&db=bsu&AN=97983333&site=ehost-live&scope=site
Learning Activities (Nongraded) Nongraded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. Review the vector-borne diseases and toxic materials in your community. Which of these affect your community the most? Create an action plan to make these issues better.
