Solvents and Solutions: Study Unit 3

• Study unit 3 focuses on solvents

Class Schedule

• Monday, April 8: (Face-to-face classes suspended) SU 2
• Wednesday, April 10: (Face-to-face classes suspended) SU 3
• Thursday, April 11: (Face-to-face classes suspended) SU 3
• Monday, April 15: Assignment 2 (Pesticide video/presentation), Revision/facilitation - SU 1
• Wednesday, April 17: SU 3
• Thursday, April 18: Facilitation – SU 1
• April 22 - May 3: SEMESTER WEEK
• Monday, May 6: Revision SU 2
• Wednesday, May 8: Revision SU 3
• Thursday, May 9: Class test 2 (SU 2 & 3), Revision of all study units, EXAMINATIONS

Learning Outcomes

• Describe the distribution of solvents in the environment
• Describe the toxicokinetics of solvents and factors making subpopulations more susceptible
• Compare the toxicity of various solvents
• Evaluate solvent misuse

Solvents and Solutions

• A solvent is a substance that dissolves a solute, resulting in a solution
• Opgeloste stof + oplosmiddel = oplossing (Solute + solvent = solution)
• Solutions can be solid/solid, gas/gas, or gas/liquid

Introduction to Solvents

• Solvents are liquid organic chemicals that exhibit variable lipophilicity and volatility
• They have small molecular sizes and lack charge
• They dissolve, dilute, or disperse other substances, typically those non-water soluble

Organic vs Inorganic Solvents

• Organic solvents contain carbon and are volatile organic compounds (VOCs)
• Inorganic solvents do not contain carbon
• Organic solvents are used as degreasers, in paints, varnishes, lacquers, inks, aerosol sprays, colorants, and adhesives
• Additionally organic solvents are used in intermediary chemical syntheses, and as petrol and petrol additives

Properties and Uses

• Variable lipophilicity increases as molecular mass (MM) increases
• Variable volatility decreases as MM increases
• Solvents can be absorbed into the body
• Absorption occurs through the lungs, skin, and gastrointestinal tract
• This is due to high lipophilicity and no charge

Solvent Characteristics

• Solvents are derived from petroleum through gasification of coal
• Naphthas and petrol are complex mixtures of over 100 compounds
• Solvents are classified by functional groups, including aliphatic and aromatic hydrocarbons, alcohols, ethers, esters/acetates, amides/amines, aldehydes, and ketones
• RGCA has respiratory and BEI limits for solvents, with Sk notation indicating skin exposure.

Toxicity

• Toxicity is determined by the number of carbon atoms, single/multiple bonds, structure (straight, branched, or ring), halogenation, and functional groups
• Toxicity is also impacted by the route/duration/frequency of exposure, and individual susceptibility
• Real-world exposure typically involves mixtures, resulting in additive, synergistic, or antagonistic effects

Example: Trichloroethylene (TCE) vs. Ethanol

• Trichloroethylene(TCE) is highly toxic
• Ethanol is less toxic

General info on Solvents

• All solvents are toxic, however, their effects vary
• Most induce narcosis, respiratory irritation, and mucus membrane irritation
• Solvents are carcinogenic to animals, but less so to humans
• The toxicity varies by solvent, e.g., Benzene has an exposure limit of 5 ppm, while Acetone's is 1000 ppm

Chronic Encephalopathy

• Solvent exposure can induce chronic encephalopathy
• Acute, high-level exposure leads to SSS depression and permanent neurological damage
• Chronic, low-level exposure carries a risk of Painter's syndrome

Painter's Syndrome

• Painter's syndrome involves organic solvent and psycho-organic syndromes
• It is a form of chronic solvent encephalopathy (CSE)
• Non-specific symptoms include headaches, fatigue, mood disturbances, and sleep disorders

Painter's syndrome: Reversible vs Severe

• Reversible form = Neurasthenic syndrome with only symptoms
• Severe form = Changes in neuropsychological function, that is not always reversible
• Oplosmiddelmisbruik- selfstudie
• Solvent abuse - self study
• Controversial if short term high levels of exposure or chronic, low level exposure leads to neurological dysfunction

Exposure

• Omgewingsblootstelling / Environmental Exposure
• Figuur 24-1 shows the relationship between the atmosphere and exposure of VOC's

Routes of Exposure

• Environmental exposure to solvents can occur through evaporation
• VOCs (volatile organic compounds) found as aerosol propellants, in thinners, and in cleaning detergents
• Atmospheric concentrations of VOCs are typically low
• Depending on water solubility, solvents can end up in drinking water
• Career exposure can happen with "confined spaces" i.e. methane gas in sewage systems

Toxicokinetics

• Volatility and lipophilicity determine absorption and distribution of solvents
• Volatile Organic Compounds (VOCs) are evaporative organic chemicals in household products that cause indoor air pollution, leading to health issues and potential liver damage. The Clean Air Act aims to reduce emissions.

Factors in Dermal Absorption

• Rate determined by solvent concentration, exposed surface area, exposure time, integrity of skin, thickness of stratum corneum, and lipophilicity
• Good absorption from GIT and is 100% of oral dose

Transport and distribution

• Portal veins, liver, heart, lungs is the passage
• There is a possibility of hepatic first elimination

Hepatic and Pulmonary First Elimination

• Hepatic first elimination = Depends on the chemical, and the rate/time it arrives in the liver
• Pulmonary first elimination = A fixed % exits pulmonary blood all times during circulation

Biotransformation

• Biotransformation to water is the goal for water excretion in the urine or bile
• It may also convert them to cytotoxic/mutagenic
• Substances include: Benzene, Toluene, Carbon tetrachloride

Elimination

• Varies considerably
• Exhalation determined by: pulmonary blood flow, blood:air PC, ventilation rate
• Readily exhaled = volatile, lipophilic VOC's

Sensitive Populations

• Considers endogeneous and exogeneous
• Also Body fat, and Respiration rate as important factors

Endogenous Factors Affecting Toxicity

• Children: high cardiac, respiratory, and body fat composition
• Bejaardes (older people) are sensitive to ethanol
• Mense = More pulmonary ventilation, & % of body fat for storage
• Genetic polymorphisms for biotransformation

Exogenous Factors Affecting Toxicity

• Factors = exercise, ventilation rate, and blood flow to liver & kidneys?
• Consumption also affects as well like eating, alcohol and CYP450 inhibitors

Further factors affecting toxicity

• Physical activity
• Diet – food intake
• Solvent mixtures
• Reduced metabolism

Summary

• What are solvents and what are they used for?
• Explain what are the environmental factors?
• Compare endogeneous and exogeneous