1. HLTH 340 Lecture A1W2013 1 HLTH 340 Environmental Toxicology and Public Health Dr. Stephen McColl Health Studies and Gerontology Program School of Public Health and Health Services NOTICE: These materials are subject to Canadian copyright and are presented here as images published in journals and books for which the University of Waterloo holds a licensed electronic subscription. These materials are provided to HLTH 340 students for their exclusive use though a non-public courseware system (UW- LEARN) and the images are restricted to the use of HLTH 340 students. Reproduction, transmittal, copying, or posting of these images by students in any form, electronic or physical, is strictly prohibited.

2. HLTH 340 Lecture A1W2013 2 Toxicology is arguably the oldest scientific discipline, as the earliest humans had to recognize which plants and fungi were safe to eat. Approximately 100,000 chemicals currently in use worldwide, 500 new chemicals enter the market- place annually. Humans are exposed to chemicals both deliberately and inadvertently. Most exposure of humans to chemicals is via naturally occurring compounds consumed in the diet from food plants. Human exposure to toxic substances goes back a long way

3. HLTH 340 Lecture A1W2013 3 Sources of environmental exposures

4. HLTH 340 Lecture A1W2013 4 Environmental challenges and human defense systems

5. HLTH 340 Lecture A1W2013 5 Route of exposure The ROUTE (site) of exposure is an important determinant of the ultimate DOSE – different routes may result in different rates of absorption. –Dermal (skin) –Inhalation (lung) –Oral (GI) –Injection The ROUTE of exposure may be important if there are tissue-specific toxic responses. Toxic effects may be local (in a specific tissue) or systemic (throughout the organism)

6. HLTH 340 Lecture A1W2013 6 Basic terminology for describing environmental chemicals endogenous (intrinsic) denotes a substance made within the organism exogenous (extrinsic) denotes a substance entering from outside the organism endobiotic any endogenous or exogenous substance normally found within the organism xenobiotic any exogenous substance not normally found within the organism constituent any exogenous substance that is contained in food or drinking water nutrient any constituent contained in food that is needed to support life (some nutrients may be toxic at excessive levels of intake) non-nutritive constituent any constituent contained in food that is not needed to support life, but is thought to be harmless (but may sometimes affect biochemical processes in a beneficial or harmful way) pollutant (contaminant, residue) any unintended exogenous xenobiotic that is considered potentially undesirable to human or ecosystem health additive any intended exogenous xenobiotic that is considered potentially desirable in food or water (may have unintended and undesirable health effects) toxicant any constituent, nutrient, or contaminant that is potentially hazardous to health natural any substance produced by non-human activity (can be beneficial or or harmful) anthropogenic any substance produced by human activity (can be beneficial or or harmful)

7. HLTH 340 Lecture A1W2013 7 Public health approaches to toxicology: environmental stressors and allostasis