Quiz 4 - Chemistry of the environment - toxicology

quiz 4 study materials

Quantitative Structure-Activity Relationship (QSAR)

software that assigns expected toxicity values to each part of a molecule to determine toxicity of the the whole molecule; does not account for interaction of chemicals

Synergism

the effect of a combination of toxins is greater than would be expected from the sum of the toxins individually; sum of parts is greater than the whole

antagonism

the effect of a combination of toxins is less than would be expected from the sum of the toxins individually

Routes of exposure for toxins

1. gastrointestinal absorption
2. dermal absorption
3. Respiratory inhalation

What can be **gastrointestinally absorbed**?

* asprin, ibuprofen, naproxen
* major route for the absorption of nutrients and water into the body

What can be dermally absorbed?

solvents, pesticides, biocides, cosmetology products, metals, pharmaceuticals

7 Classifications of toxins

1. respiratory toxins


1. general metabolic toxins
2. neurotoxins
3. endocrine system toxins
4. allergens
5. carcinogens
6. mutagens
7. teratogens

Sulfur dioxide

* type: respiratory toxin
* description: respiratory tract irritant, damages lung tissue, increased airway resistance
* Risks: long-term exposure to low levels leads to increased risk of health problems
* also toxic to plants (early insecticide)

nitrogen dioxide

* type: respiratory toxin
* description: causes inflammation of lung tissue
* Risks: may have long-term effects on ability to fight lung infections
* bronchiolitis fibrosa obliterans; silo-filler’s disease
* dangerous to humans at high concentrations

ozone

* type: respiratory toxin
* description: pungent bluish gas; coughing; shortness of breath; nose and throat irritation; lungs produce fluid
* causes plants to be more susceptible to diseases

allotropes

from of an element that differs from other forms of same element in its molecular arrangement

particulates

* type: respiratory toxin
* description: result of indoor and outdoor air pollutions such as dust, combustion, and smoke
* silicosis; asbestosis; brown lung (cotton); farmer’s lung (hay mold); black lung (coal dust)

general metabolic toxins

* interfere with some essential biochemical process
* includes toxins with multiple modes of action
* effects can be massive and immediate or slow and cumulative
* carbon monoxide

carbon monoxide

* type: general metabolic toxin
* description: disrupts hemoglobin carrying oxygen in blood

nitrate

* type: general metabolic toxin
* description: converted to nitrite ions in the body, oxidizes Fe^2+ in hemoglobin to form methemoglobin
* blue-baby syndrome

heavy metals

* type: general metabolic toxin
* description: react with sulfhydryl groups which can deactivate enzymes
* mercury: most toxic in compounds; vapor is toxic when oxidized in body; in light up shoes; vapor and mercury compounds such as fungicides for grain
* lead: causes brain, liver, and kidney damage; treatment involves chelating agents; exposure to lead as well as its compounds is unsafe
* Cadmium: can replace calcium in bones; severe abdominal ain, vomitting, and diarrhea; 30 year half-life in body

arsenic

type: general metabolic compound

description: inactivates enzymes by binding with sulfhydryl groups

symptoms: vomiting, diarrhea, abdominal pain, esophageal pain, vasodilation, heart-rate depression

pesticides

substances that kill or otherwise control unwanted organisms

insecticides

pesticide to kill insects

herbicides

pesticides to kill palnts

fungicides

pesticides to control growth of fungi

DDT

* organochlorine pesticide (insecticide)
* no apparent effect on humans
* controls mosquito-borne diseases
* various species developed resistance
* caused soft shells in eagles
* eventually banned in the US

PCBs (polychlorinated biphenyls)

* developed in 1930s as transformer insulator
* little acute toxicity in humans
* chronic toxicity possible but not proven
* chloracne is definite symptom but not fatal

Dioxins

* variety of polychlorinated benzodioxins commonly formed as byproducts in reactions involving chlorinated hydrocarbons
* similar structure to PCBs
* no known use
* Agent orange in Vietnam war
* severely toxic in small animals
* TCDD poisoned Ukrainian presidential candidate

Neurotoxins

* disturb the chemical processes occurring at the synapse during nerve signal transmission
* most effect cholinergic nerves (things you don’t think about) that use acetylcholine as neurotransmitter
* inhibit synthesis of acetylcholine; block the receptor; or permanently turn on nerve
* interfere with the Acetylcholine cycle

acetylcholinesterase poisons

* type: neurotoxin
* inhibit enzyme cholinesterase that breaks down acetylcholine
* many widely used insecticides (very environmentally important)
* can be ingested or absorbed through the skin
* parathion, malathion
* nerve gas sarin in WWII
* one drop can kill person

Endocrine hormones

* hormones in an organism that are produced by endocrine glands into bloodstream
* eventually attach to receptors on certain cells in the body to produce a response

environmental estrogens

* type: endocrine toxin
* synthetic chemicals that can mimic naturally occuring estrogens
* greatest effects in wildlife like fish
* PCBs dioxins, pesticides, BPA(?)
* feminization of males, disruption of reproduction, effects on fetal development

phytoestrogens

* endocrine disruptor
* in plants
* implicated in some problems
* found in soy

Allergens

* large class of compounds that activate and overstimulate the **immune system**
* ex: formaldehyde

carcinogens

* cause cancer
* uncontrolled cell growth
* cells lose functional identity and locational restriction
* seem to require repeat exposure
* benzo(a)pyrene; 2-naphthylamine
* not all are synthetic chemicals

mutagens

* chemicals that damage or alter the genetic information in cells
* closely related to carcinogens
* of great concern when interfering with reproductive cycle
* difficult to determine causes
* benzo(a)pyrene; ozone

teratogens

* induce **birth defects** by causing direct damage to a developing embryo
* Cannot be classified as mutagens because they DO NOT act by disturbing genetic material in cells
* of most concern during embryonic stage of pregnancy when critical organs are formed
* alcohol, acutane, arsenic, lead, mercury, PCBs, thalidomide

Diethylstilbestrol (DES)

* type: tereatogen
* synthetic estrogen-like molecule that could be ised as natural estrogen substitute
* used to suppress lactation
* was used to decrease likelihood of miscarriages until female children began to develop clear cell adenocarcinoma CCA

persistents

toxins that do not break down in the environment

3 ways chemicals in the environment break down

1. hydrolysis
2. ultraviolet light
3. mircoorganisms

bioaccumulation

* the accumulation of toxins in the fat of an organism that results from the organism coming into contact with water containing toxins
* in ONE organism

biomagnification

* the increase in the concentration of fat-soluble toxins as one moves to higher levels of the food web
* concentrations of some toxins increase going up the food chain

catalysts

substances that speed up a reaction without being used up in the reaction

The author of the ground-breaking book, Silent Spring, which sounded an alarm concerning risks to the environment, was

Rachel Carson