ENSP101 Chapter 8 Environmental Health and Toxicology 8 1 Environmental Health Health a state of physical and emotional well being the absence of disease or ailment Disease a deleterious change in the body s condition in response to destabilizing factors such as nutrition chemicals or biological agents Diet and nutrition infectious agents toxic substances genetics trauma and stress all play roles in morbidity illness and mortality death Environmental health the science of external factors that cause disease including elements of the natural social cultural and technological worlds in which we live Public health successes o Smallpox was completely wiped out 1977 o Polio has been eliminated everywhere in the world except for a few remote villages in northern Nigeria o Epidemics of typhoid fever cholera and yellow that regularly killed thousands of people in North America a century ago are now rarely encountered o AIDS which once was an immediate death sentence has become a highly treatable disease to 64 3 years disability die wealthy people o The average HIV positive person in the US now lives 24 yrs after diagnosis if treated faithfully with modern medicines o During the 20th century world average life expectancies more than doubled from 30 A vital component of rising life expectancies is declining child mortality Disability adjusted life years DALYs a measure of premature deaths and losses due to illnesses and diabilities in a populations o DALYs combine premature deaths and loss of a healthy life resulting from illness or o This is an attempt to evaluate the total cost of disease not simply how many people The world is now undergoing a dramatic epidemiological transition o Chronic conditions such as cardiovascular disease and cancer no long afflict only o Although the traditional killers in developing countries infections maternal and perinatal birth complications and nutritional deficiencies still take a terrible toll diseases such as depression and heart attacks hat once were thought to occur only in rich countries are rapidly becoming the leading causes of disability and premature death everywhere By 2020 its expected that 15 million people will have cancer and 9 million will die from it A silent epidemic of diabetes is now sweeping through our population o Obesity diets high in sugar and fat lack of exercise and poverty which encourages fast food intake and makes health food unavailable all play important roles in this disease o Blindness circulatory problems and kidney failure are common results of severe uncontrolled diabetes o 70 of all lower limb amputations are diabetes related Taking disability as well as death into account in our assessment of disease burden reveals the increasing role of mental health as a worldwide problem Although the ills of modern life have become the leading killers almost everywhere in the world communicable diseases still are responsible for about 1 3 of all disease related mortality Better nutrition clean water improved sanitation and inexpensive inoculations could eliminate most of those deaths A wide variety of pathogens disease causing organisms afflict humans including viruses bacteria protozoan s single celled animals parasitic worms and flukes Influenza is caused by a family of viruses that mutate rapidly and move from wild and domestic animals to humans making control of this disease very difficult Every year there are 76 million cases of food borne illnesses in the US resulting in 300 000 hospitalizations and 5 000 deaths o Both bacteria and intestinal protozoa cause these illnesses o They are spread from feces through food and water Malaria is one of the most prevalent remaining infectious diseases o Every year about 500 million new cases of this disease occur and about 2 million people die form it o The territory allows mosquito vectors to move into new territory Emergent diseases a new disease or one that has been absent for at least 20 years o E g swine flu in US cholera in South America TB in Russia o Rapid international travel makes it possible for these new diseases to spread around the world at jet speed The largest recent death toll from an emergent disease is HIV AIDS Domestic animals and wildlife also experience sudden and widespread epidemics which are sometimes called ecological diseases o Ebola hemorrhagic fever kills up to 90 of its victims o Chronic wasting disease CWD o Transmissible spongiform encephalopathies TES that include mad cow disease in cattle scrapie in sheep Climate change also facilitates expansion of parasites and diseases into new territories Tropical diseases such as malaria cholera yellow fever and dengue fever have been moving into areas from which they were formerly absent as mosquitoes rodents and other vectors expand into new habitat o This affects other species besides humans One thing that emergent diseases in humans and ecological diseases in natural communities have in common is environmental change that stresses biological systems and upsets normal ecological relationships We are coming to recognize that the delicate ecological balances that we value so highly and disrupt so frequently are important to our own health Conservation medicine is an emerging discipline that attempts to understand how our environmental changes threaten our own health as well as that of the natural communities on which we depend for ecological services Resistance to drugs antibiotics and pesticides is increasing The heaviest burden of illness is borne by the poorest people who can afford neither a healthy environment nor adequate health care o Estimates that 90 of all disease burden occurs in developing countries where less than 1 10 of all health care dollars are spent o Worldwide only 2 of the people with AIDS have access to modern medicines o Every year some 600 000 infants acquire HIV almost all of them through mother to child transmission during birth or breast feeding o Improved health care in poorer countries may also help prevent the spread of emergent diseases in a globally interconnected world 8 2 Toxicology Toxicology the study of toxins poisons and their effects particularly on living systems Toxins damage or kill living organisms because they react with cellular components to disrupt metabolic functions o Because of this reactivity toxins often are harmful even in extremely dilute concentrations All toxins are hazardous but not all hazardous materials are toxic o Many of these materials must be