Environmental Toxicology Final Exam Review

hematotoxicant

A ____________ is a toxicant that either interferes with hematopoiesis or affects the viability of red blood cells, which can result in anemia and hypoxia (lack of oxygen).

c, d, e

A lab conducted toxicity tests with two different amphipod species. Amphipod A is maintained in water at 5°C, while amphipod B is kept in water at 20°C. Both species are exposed to the same non-polar hydrophobic chemical at the same concentration range for 96 hours. At the end of exposure, all individuals in A survived and no LC50 could be obtained, while the 96 h LC50 for amphipod B was found to be 10 μg/L. How would you explain this difference in toxicological response? (Note the answer(s) are not the only possible explanations). a. Species A is tolerant to the test chemical. b. Species B is much more sensitive to the test chemical than species A. c. Species A reached a lower internal concentration than species B. d. Species B reached a higher internal concentration than species A. e. Species A requires a longer exposure duration to reach the same internal concentration as B.

neuropathy

A large number of chemicals are known to result in toxic ____________, including metals (aluminum, arsenic, lead, manganese, mercury, methyl mercury), industrial compounds (trimethyltin), pharmaceuticals and solvents.

myelinopathy

Myelin provides electrical insulation of neuronal processes, and its absence leads to a slowing and/or aberrant conduction of electrical impulses. In ____________, some toxicants can interfere with myelin maintenance or function.

maximum cumulative ratio

The ____________ ____________ __________ (MCR) is defined as the ratio between the observed cumulative toxicity and the maximum toxicity caused by one chemical.

ambient, biologically effective

The ____________ chemical concentration does not cause the effect. It is the ___________ ____________ concentration within the organism that causes the effect. As this internal concentration is determined by toxicokinetics, the factors that influence these processes (uptake, metabolism, distribution and elimination) also influence the observed response for a given scenario

filter, blood, homeostasis

. The principal role of the kidneys is to ____________ the ____________ and maintain total body ____________.

logarithmic

.A dose-response curve plots the response (e.g., death or a sublethal effect) of a population under study (e.g., fish, rats, cells, enzymes) against increasing dose (or concentration) of the test chemical applied to the system, usually on a _______________ scale

infection, parasite

.A number of pesticide compounds have been proven to affect immune parameters, and some cases of immunosuppression (exerted by organochlorine pesticides, organophosphates, carbamates, atrazine, and 2,4-D) were correlated to higher susceptibility of organisms to ____________ and ____________ -caused diseases.

continuum, toxicity

.Chemically induced effects at low levels of biological complexity (e.g., molecular and cellular) can translate into higher order effects at the tissue, organ and eventually organism level, depending on the severity of the effect and the ability of compensation and repair mechanisms to cope with the damage. This is known as the ____________ of ____________.

axonopathy

.In ____________, some toxicants can "cut" the axon, resulting in a physical break in neuron transmission. Many chemicals have been linked to this effect, including metals (gold and platinum), alkaloids, pharmaceuticals, industrial compounds (acrylamide), solvents and pesticides.

lethal, effective

.The benchmarks for mortality or sublethal effects (in 50% of the test population) are usually expressed as ____________ concentration (LC50) or ____________ concentration (EC50).

suspended solids, organic, nutrients

.The main purpose of secondary treatment is to remove ____________ ____________, dissolved ____________ matter and ____________ to avoid eutrophication of receiving waters.

50

.While it has been established that the mixtures of compounds at concentration levels that are well below observable effect levels may produce substantial mixture toxicity, there are no studies in the literature that tackle defined mixtures of more than _____________components.

whole effluent toxicity, ambient, discharge

.__________ ____________ ____________ (WET) refers to the combined toxicity of the mixture of all micropollutants in an effluent sample to aquatic organisms using a suite of standardized aquatic toxicology assays. It can be used as a monitoring tool, testing ____________ water that has or is suspected of receiving a chemical pollutant _________.

teratogens

.____________ are compounds that cause birth defects and can lead to pre- and postnatal mortality.

foetotoxic

.____________ chemicals affect the conceptus from the fetal stage onwards (usually after 8 weeks in humans).

hypersensitivity

.____________ reactions (allergies) result from the immune system responding in an exaggerated or inappropriate manner (e.g., penicillin).

sex hormones

._____________ ___________ (androgens and estrogens) are particularly important in fetal reproductive organ development, puberty and sexual maturation. Toxicants such as PCBs, DDT/DDE, brominated flame retardants, dioxins, hexachlorobenzene, personal care products and heavy metals have been linked to reproductive abnormalities

c

A recombinant cell is: a. A native cell. b. A native cell that has been accidentally immortalized. c. A genetically modified cell. d. Two native cells combined to one cell.

membrane receptors

A very wide range of toxicants have been shown to suppress or stimulate the immune system, including PCBs, PAHs, pesticides, metals, solvents, hormones, pharmaceuticals and UV radiation. Some toxicants (e.g., sulfamethoxazole) can stimulate immune cells directly by binding to their ____________ ____________.

b, c, f

Bioanalytical tools are: a. All in vivo and in vitro assays used in effect-based water quality monitoring. b. Mostly cell-based in vitro assays used in effect-based water quality monitoring. c. Time- and cost-efficient techniques. d. Very time consuming and expensive. e. Only able to detect the same known chemicals as chemical analysis. f. Able to detect the responses of unknown compounds. g. Able to detect the responses of unknown compounds but cannot account for mixture toxicity.

genotoxic, epigenetic

Chemicals that induce cancer have been broadly classified in two categories: i) ____________ carcinogens (e.g., PAHs) that interact physically with DNA to alter or damage its structure, and ii) ____________ carcinogens that impact DNA expression through DNA methylation, protein phosphorylation and receptor-mediated effects, without directly affecting DNA structure

a, c, d, g

Circle the correct responses. The Tissue Residue Approach : a. Assesses effect relative to tissue concentration. b. Can only be used to assess effects to tissue. c. Can be used to assess the same effects as standard approaches. d. Applies the same principle model for concentration-response assessment, the only difference being the internal concentrations used. e. Applies a completely different model for concentration response assessment. f. Is particularly useful for standard tests. g. Enables direct comparison of toxicological sensitivity despite differences in toxicokinetics. h. Toxicokinetics are not important for toxicity testing.

target, non-target

Currently used pesticides are mainly designed on the basis of their desired mode of action, which is aimed at displaying optimal efficiency in _____________ organisms and minimum side effects in _____-__________ organisms.

modes, independent action

Even for chemicals that act according to different ____________ of toxic action, mixtures of more than 10 compounds at low effect level have shown measurable effects, which were consistent with the prediction obtained from the _______________ _____________ (IA) model.

synergistic action

Global warming is decisively expected to affect the ecotoxicological potency of pesticides, because 83% of ecotoxicological studies on the combined effects of elevated temperature and pesticide exposure have revealed the ___________ _____________ of these factors.

repeated exposure

Highly lipophilic compounds that are resistant to biotransformation (such as polyhalogenated biphenyls and chlorinated hydrocarbons) are very hard to eliminate and tend to accumulate in the body upon ____________ ____________

IEC50, ILC50

How do you designate an internal effect concentration, i.e., what are the acronyms for the internal EC50 and LC50?

concentrations, toxicity

In Mixture Toxicity, single chemical ______________ are often below any _____________ threshold, but the effect of the mixture may exceed thresholds.

neurotransmitter

In _______________-associated toxicity, a wide range of naturally-occurring toxins as well as pesticides and pharmaceuticals can inhibit normal neurotransmitter function. Organophosphorus and carbamate pesticides, for example, inhibit the enzyme acetylcholinesterase, which is responsible for recycling the neurotransmitter acetylcholine.

in-situ testing, exposure

In a form of WET referred to as ______-__________ ____________, caging experiments typically involve a series of cages from the point of discharge to a predicted safe distance downstream in a river or beyond the mixing zone in the case of lakes and ocean outfalls. After an appropriate period of ____________ (determined by site and species), the animals are brought back to the laboratory and examined for effects.

endocrine, reproductive

In birds, although acute mortality could be attributed to inhibition of acetylcholine esterase activity exerted by organochlorines, organophosphates, and carbamates, chronic exposure via oral uptake to organochlorines, organophosphates, carbamates and a variety of herbicides and fungicides, resulted in disturbances of the ___________ and ____________ systems.

low, mixture

In some ecotoxicological studies, mixtures of chemicals at concentrations too __________ to cause effect on their own can lead to appreciable ___________ effects, and often in good accordance with predictions by the principles of CA/DA.

point sources, non-point

In the earlier years of the Clean Water Act there was a focus on regulating discharges from '____________ ____________ such as municipal sewage treatment plants and industrial facilities. Since the 1980s efforts to reduce ______-___________ source pollution have been introduced including cost sharing with landowners as a key tool.

hormone catabolism

Increased ____________ ____________ (destruction) is when toxicants that induce liver enzymes (e.g., phenobarbital, benzodiazepines, DDT, chlorinated hydrocarbons) can increase the rate of conjugation and excretion of hormones such as T3 and T4. (form of endocrine toxicity)

ion channels, calcium, electrical excitability

Many substances can cause cardiac toxic responses, mostly by affecting ______ ______ , ____________ ion homeostasis, and ____________ ____________ and action potential generation

lymph, blood

Once taken up by the organism, chemicals are distributed via the __________ and __________ stream to organs and various tissues ultimately reaching the target cells.

fish embryo toxicity

One form of WET, the ____________ __________ __________ (FET) test has been applied to investigate the success of the different steps of wastewater treatment, which can be grouped into primary, secondary and tertiary treatment.

invertebrates, butterflies

Other prominent indirect pesticide effects act on food webs and species competition through the removal of prey or competing species. Herbicides, which reduce the plant cover of soil and change plant species diversity, were found to be responsible for reduced food availability and thus adverse secondary effects on soil ___________ and _____________.

physiological tolerance

Pesticide interactions with global warming will probably influence the direction in which selection acts upon biota, a factor that will be particularly problematic for populations or species living at the edge of their _____________ ____________.

reference

Potency evaluation is useful to compare individual compounds and of samples of unknown composition. Knowing the potency of a range of similarly acting compounds, it also possible to predict the potency of their mixtures. Potency is typically expressed relative to a _____________ compound for which the toxic mode of action in question is well described.

settling, skimming

Primary treatment generally includes only ____________ and ____________.

one sole, dominant

Risk assessment focusing on single chemicals can only be justified if ____________ ____________ chemical is responsible for the total mixture toxicity, while all other compounds are inert or their combined mixture effect is no larger than the toxicity of the _______________ component

biological

Secondary treatment is often referred to as ____________ treatment and typically includes aeration, biological degradation and mechanical filtration.

potable

Secondary treatment may be appropriate for, e.g., golf course irrigation and removes some micropollutants, but additional treatment is necessary to improve micropollutant removal prior to ____________ reuse.

lowest observed effects concentration, lowest

The __________ __________ __________ __________ (LOEC) is the __________ concentration tested that produces a significant deviation from the control.

no observed effects concentration, highest

The __________ __________ __________ __________ (NOEC) is the ____________ tested concentration that does not produce an effect significantly different from the control.

hormesis

Some chemicals that cause toxicity at high concentrations can exhibit a stimulatory effect at low concentrations. This phenomenon is known as ____________.

vascular, vasoactive

Specific ____________ toxicity can occur from damage to either epithelial cells (e.g., aspirin, endotoxins, carbon monoxide) or smooth muscle cells (e.g., metals interfering with calcium homeostasis) or from exposure to ____________ compounds.

activated carbon, chlorination, ozonation, reverse osmosis

Tertiary treatment refers to advanced processes such as ____________ ____________ treatment, advanced filtration, ____________ (Cl), ____________ (O3), UV treatment and ____________ ____________ (RO).

concentration, lifetime, non-carcinogenic

The Safe Drinking Water Act defines the Drinking Water Equivalent Level (DWEL) as the ____________ in drinking water that over ______________ exposure is protective of human health, at least for threshold chemicals (i.e., _____-____________ chemicals).

concentration, TEF

The TEQ is the sum of the ____________ of each chemical in a mixture multiplied by their _____________ values, and is the "apparent concentration" as if all of the chemicals in the mixture were fractions of the most toxic chemical:

toxic equivalency factors, parallel

The concept of ____________ ____________ ____________ (TEF) is an extension of the mixture concept of CA/DA and is only applicable for groups of chemicals with a common mode of toxic action (MOA). This is a special case of CA/DA and the condition of ____________ concentration-response curves must be fulfilled.

generation, microevolutionary

The elucidation of long-term pesticide effects in communities of animals and plants is often hampered by the long ___________ times of the species involved. In contrast, microbial communities display ___________ responses within a rather short time period.

neuron, axon, myelinating, neurotransmitter

The four most common targets of neurotoxicants are the ___________, the ____________ (the neuron's projection towards other neurons), the ____________ cell and the ____________ system.

quarter, cardiac

The kidneys are particularly sensitive to blood-borne toxicants as they receive about a ____________ of the ____________ output.

concentrations, toxicants

The liver is the main organ where exogenous chemicals are metabolized to make them more hydrophilic for excretion. As a consequence, liver cells can be exposed to significant ____________ of ____________.

lipophilic toxicants

The main purpose of first-pass metabolism is to make ____________ ____________ more water-soluble, which will facilitate their excretion.

small intestine

The majority of ingested toxicants will be absorbed in the ____________ ____________, which has a very large specialized surface area making it very efficient at absorbing nutrients and toxicants from food.

constant renewal

The most appropriate exposure systems for hydrophobic chemicals in water are flow-through systems and passive dosing approaches, which allow ____________ ____________ of the test solution.

cytotoxic interferences

The presence of a chemical can cause induction of metabolic enzymes. The initial increase in enzyme induction with increasing chemical concentration will be followed by a decreasing response at the higher concentration range. This type of dose-response curve is indicative of ____________ ____________, where total enzyme activity decreases at higher doses because the toxicant is becoming cytotoxic.

endocrine

The spill of highly persistent organochlorines (DDT and its metabolites, diclofol, dieldrin, and toxaphene) in Lake Apopka, Florida in 1980 is well known as an example linking the ____________ effects of pesticides to juvenile population densities and unexpected adult mortality in wildlife reptiles.

upper exposure limits

Water quality standards are ____________ ____________ ____________ that are included in legislation. These standards are derived from scientifically based water quality criteria, by application of safety factors and by political decision.

b, c, d

What is the purpose of cytotoxicity monitoring in bioanalytical tools. a. No purpose. It is much better to include a specific assay. b. Cytotoxicity is used as a measure of baseline toxicity. c. Cytotoxicity is used as an integrative measure of all toxicity pathways in the cell. d. Cytotoxicity should be monitored for QA/QC to account for potential overlap/masking of specific responses.

excessive stimulation

___________ ____________ can cause hyperplasia (excessive cellular development) and hypertrophy (gross enlargement) of individual endocrine organs, and eventually lead to tumor development. (form of endocrine toxicity)

basal cytotoxicity

___________ ____________ may be described as any general cellular-level effect that leads to dysregulation of on-going cellular activity, impairment of cellular maintenance, dysregulation of gene expression and/or physical damage to cell structures.

embryotoxic

___________ chemicals affect the conceptus prior to the fetal stage (usually up to 8 weeks in humans).

chronic toxicity

____________ ____________ should be taken into account for all pesticides that are applied at regular intervals, particularly those that are highly persistent, such as organochlorines.

static exposure

____________ ____________ tests do not renew the test solution during the test.

static renewal

____________ ____________ tests renew the test solution (or sometimes 80% of it) at set time points throughout the test (for example, every 24 hours).

immunosupression, immunostimulation

____________ results in reduced efficacy of the immune response (i.e., impaired resistance), while ____________ stimulates the immune system, which may result in excessive immune response.

interference

____________ with hormone synthesis or secretion, as seen for some pharmaceuticals (form of endocrine toxicity)

hormone signaling

one mechanism of endocrine toxicity is interference with ____________ ____________ (endocrine disruption).

synergism

total toxicity units for a mixture being less than 1

antagonism

total toxicity units for a mixture being more than 1