class: center, middle, inverse, title-slide # Epidemiology, Toxicology, and EHRA ## A Review ### Arindam Basu ### (updated: 2021-09-12) --- # Environmental Epidemiology, Environmental Toxicology,and EHRA --- # Recap of everything we have learned so far - Concept of Environmental Health - Environmental Epidemiology - Environmental Toxicology - Going forward: - Environmental Health Risk Assessment --- # Concept of Environmental Health Which of the following is **NOT** an example of an Environmental Health problem? - Social deprivation and stunting in children - Water contamination and diarrhoea - Soil contamination with nitrate and cancer --- # Correct Answer > Social deprivation and stunting in children - This is NOT ENVIRONMENTAL HEALTH - This is an example of SOCIAL DETERMINANTS ofHEALTH - It may seem: - Social deprivation is outside of humans - Social deprivation is within the control of human intervention - Reason: - Social deprivation is not a TANGIBLE entity --- # Which of the following is/are NOT Environmental Health? - (a) Rheumatic Fever caused by Group A Streptococci - (b) Poor housing conditions that lead to Rheumatic Fever - (c) Poverty leading to skin infections leading to rheumatic heart disease --- # Correct answer - (a) and (c) ARE NOT examples of Environmental Health - (b) is ENVIRONMENTAL HEALTH - (a) is INFECTIOUS DISEASE - (c) is SOCIAL DETERMINANT of health --- # Review of Epidemiology - ### Prevalence - ### Incidence - ### Study designs --- # Prevalence > In a Town T, there are 400 residents. 20 of them have an unknown fever ("FUO"). What is the prevalence of FUO in Town T (calculate in number of people per 1000)? --- # Answer to Prevalence - The prevalence of FUO in Town T is: ``` ## [1] 50 ``` --- # Concept of prevalence - Number of people with the Disease ("D") - Total number of people ("N") - If the Base population is "B" (such as 100, 1000, etc) - **Prevalence = (D / P ) * B** --- # Worked out solution - Here, "D" = 20 - "N" = 400 - "B" = 1000, - Therefore, Prevalence = (20 / 400) X 1000 = = **50 per 1000** --- # Prevalence is a Proportion - We measure prevalence as ONE time - Prevalence is calculated based on cross-sectional surveys --- # Incidence - Number of **NEW CASES of a HEALTH CONDITION** - Population-Time (Person-Time) --- # What is incidence: consider the data | year| population| time_period| cases| at_risk| cumulative_cases| |----:|----------:|-----------:|-----:|-------:|----------------:| | 2001| 1000| 0| 10| 1000| 10| | 2002| 1000| 1| 20| 990| 30| | 2003| 1000| 1| 30| 970| 60| | 2004| 1000| 1| 20| 940| 80| | 2005| 1000| 1| 10| 920| 90| --- # Explanation - We follow data between 2001 and 2005, 5 years of data - There were 1000 people, no one died, no one moved away - First year was 2001, hence follow up period is 0 - For subsequent years, we followed them for 1 year, hence 1 - Cases indicate number of existent (as in 2001) cases and - Number of new cases (from 2002 onwards) --- # Prevalence and incidence | year| prevalence_1000| incidence_1000py| |----:|---------------:|----------------:| | 2002| 30| 20.20202| | 2003| 60| 30.92784| | 2004| 80| 21.27660| | 2005| 90| 10.86957| --- # Explanation for the incidence and prevalence - For the first year, the time period of follow up is 0 - Hence the incidence is NOT ESTIMABLE and shows as inf - But for 2002 onwards, it is based on the - Number of new cases / population X time period - The prevalence in any year is based on CUMULATIVE CASES --- # Prevalence (Blue) vs Incidence (Red) <!-- --> --- # What does the graph show? - For a chronic disease such as the one shown - Incidence can increase and decrease over time - Prevalence will continue to remain high unless - People die from the disease or get cured - This is because incidence relates to NEW CASES - Prevalence is about EXISTING CASES --- # Study designs - Prevalence can be studied by **Cross-sectional surveys** - Incidence can be studied by **Prospective Studies** - In Environmental Health, many studies are **Ecological** - This means, aggregated health events and environmental data are studied --- # Toxicology - Study of toxins - Dose is the poison or toxin - Toxicokinetics - Toxicodynamics --- # Toxicokinetics - How toxins once enter the body - Moves around - Five steps - Absorption, Distribution/Storage, Metabolism, Excretion --- # Which of the following is NOT an entry point for toxin - Skin - Oral cavity (mouth/eating/drinking) - Respiratory system (breathing/inhalation) - Thinking and Brain --- # Answer to entry point - Thinking and Brain - There is NO PORTAL of entry --- # All toxins follow ADME - A: Absorption - D: Distribution and storage - M: Metabolism - E: Excretion --- # Which of the following is missing in this diagram <div id="htmlwidget-7493fa28ab8c811a49a6" style="width:504px;height:504px;" class="DiagrammeR html-widget"></div> <script type="application/json" data-for="htmlwidget-7493fa28ab8c811a49a6">{"x":{"diagram":"\ngraph TB\n A[Oral Cavity]-->B[Stomach]\n B[Stomach]-->C[Intestines]\n C[Intestines]-->D[Liver]\n D[Liver]-->M(Metabolites)\n D[Liver]-->E[Blood Stream]\n C[Intestines]-->E(Blood Stream)\n \n "},"evals":[],"jsHooks":[]}</script> --- # Answer to what is missing - Excretion - A is from Oral Cavity to Stomach to Intestines - D is via Blood Stream - M is from Liver to Metabolites - E is not shown here --- # Toxicodynamics - As the toxin circulates it can act on cells - How toxins act on cells - Toxins act being outside of cells - Toxins act after entering the inside of cells --- # Every toxin has toxicokinetics and toxicodynamics - Toxins in air - Toxins in water - Toxins in soil - Toxins in food --- # Pathways and actions of Environmental Toxins <div id="htmlwidget-f14027716fd11ec47ed9" style="width:504px;height:504px;" class="DiagrammeR html-widget"></div> <script type="application/json" data-for="htmlwidget-f14027716fd11ec47ed9">{"x":{"diagram":"\ngraph TB\n P[Pollutants]-->Air\n P[Pollutants]-->Food\n P[Pollutants]-->Soil\n Soil-->Food\n P[Pollutants]-->Water\n Air-->Lungs\n Food-->Oral\n Water-->Oral\n Lungs-->Blood\n Oral-->Blood\n Blood-->Lungs\n Lungs-->Breath\n Blood-->Kidney\n Kidney-->Urine\n Blood-->Skin\n Skin-->Sweat\n \n "},"evals":[],"jsHooks":[]}</script> --- # Toxins can be - Physical (Pressure, wind, sunlight, other light, radiation) - Chemical (Acids, bases, alkali, solvents, ...) - Biological (viruses, bacteria, fungi, plants, animals) --- # Basic concepts - Epidemiology and Experiments is about identifying Hazards - Toxicokinetics is about converting the Exposure to Dose - Toxicodynamics is about converting Dose to Risk - Assumption: Higher the dose, higher the risk --- # Relationship between Hazard and risk <div id="htmlwidget-bee53d5c798f2730db08" style="width:504px;height:504px;" class="DiagrammeR html-widget"></div> <script type="application/json" data-for="htmlwidget-bee53d5c798f2730db08">{"x":{"diagram":"graph LR\n Exposure-->Hazard\n Hazard-->Outcomes\n Outcomes-->Risk\n Exposure-->Outcomes\n \n "},"evals":[],"jsHooks":[]}</script> --- # Environmental Health Risk Assessment <div id="htmlwidget-ef24b71f8785b9c35ab0" style="width:504px;height:504px;" class="DiagrammeR html-widget"></div> <script type="application/json" data-for="htmlwidget-ef24b71f8785b9c35ab0">{"x":{"diagram":"\ngraph TD\n A[Hazard Identification]-->B[Dose Response]\n A[Hazard Identification]-->C[Exposure Assessment]\n C[Exposure Assessment]-->D[Risk Characterisation]\n B[Dose Response]-->D[Risk Characterisation]\n \n \n"},"evals":[],"jsHooks":[]}</script> --- # Hazard identification - Animal experiments - Epidemiological Studies - Characterise dose-response effects --- # Dose Response effects - Non-cancer causing toxins - Cancer causing toxins --- # Shape of cancer causing toxins  --- # Shape of non-cancer causing toxins  --- # Summary - To study environmental health - You need to know first what is NOT environmental health - You must have a good grasp of basic environmental epidemiology - You must understand the basics of toxicology - Next up, nitty gritty of environmental health risk assessment