"Wisdom begins in wonder" – Socrates
Category: Chemistry
Leachates
02/01/26
“What happens when liquid picks up dissolved/suspended solids as it moves through a permeable layer?”
Liquids can move through permeable layers. Sometimes, the layer may have soluble or suspended solids along its journey and form what’s called a Leachate. Leachate properties are dependent on the liquid and its solvent. Leachates from stormwater landing on landfills can pollute nearby surface and groundwater.
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Hazard Quotient
01/27/26
“How can we quantify the lethality of exposure to a substance?”
People are exposed to potentially hazardous substances all the time, whether it’s traces of air pollution or bacterial growth on food. We also know that if exposure breaches a certain level, it becomes dangerous. So how can we quantify the lethality of exposure to a substance? Well, what if we divide the exposure level by the reference dose? This is how the Hazard Quotient works, and it is a very useful tool in toxicology.
Chronic Daily Intake
01/23/26
“How can we calculate the amount of contaminant a person is exposed to daily?”
People are exposed to all kinds of substances throughout the day, whether it’s from the food we eat or the air we breathe. Some of these substances are harmful and can lead to health problems. We can measure how much of these contaminants we expose ourselves daily through Chronic Daily Intake. Chronic daily intake is typically expressed as milligrams of substance per kilogram of body weight per day. The US E.P.A uses chronic daily intake as part of health hazard assessment.
Plume Rise
01/22/26
“How far does air pollution rise after release from a stack?”
People often release waste air from a building stack. This air will rise to a certain height called the Plume Rise before moving in the direction of the wind. The higher the plume rises, the lower the amount of pollution that will fall on the ground. A higher exit temperature and faster exhaust speed lead to a larger sack height.
Acceptable Daily Intake (ADI)
01/21/2026
“How does the WHO measure how much a certain substance in food or drinking water can be consumed daily over a lifetime without an appreciable health risk?”
NOAELs document how much of a substance an organism can handle before a statistically significant health effect occurs. However, these studies may be conducted in controlled environments or on test animals that may not accurately reflect human conditions. To account for all of these variables, organizations such as the World Health Organization (WHO) and the European Food Safety Authority (EFSA) use Acceptable Daily Intake (ADI). Acceptable daily intake measures the amount of a certain substance in food or drinking water that can be consumed daily over a lifetime without an appreciable health risk to people. This is commonly expressed as milligrams of substance per kilogram of body weight and is applied by regulatory and health authorities all over the world to monitor food additives, pesticides, and much more. Acceptable daily intake is applied to food ingredients similar to how reference dose is applied to environmental toxins.
Reference Dose (RfD)
01/20/26
“How does the U.S. EPA produce recommended daily lifetime exposure limits for substances?”
NOAELs are the highest level of a substance a person can take without any statistically significant effects, according to research. However, this could be much higher than what may actually be safe for long-term use. The U.S. EPA has created the Reference Dose (RfD) in response. Reference does are the maximum acceptable oral dose of a toxic substance that has no adverse noncancer health effects from a lifetime of exposure. Reference doses are commonly found by dividing the NOAEL for a substance by uncertainty factors.
NOAEL – No Observed Adverse Effect Level
01/19/26
“How can we measure the highest dose of a substance that does not cause any statistically significant effect?”
People worry about whether a substance they’re exposed to leads to health complications. One way to understand this is to measure the highest dosage of the substance that organisms can handle before a statistically significant effect occurs. Labeled NOAEL – No Observed Adverse Effect Level, these measurements are fundamental for quantifying safe exposure levels for substances.
Formaldehyde
01/12/2026
“What’s so special about formaldehyde?”
Chemicals come in all sorts of forms. CH2O, also known as Formaldehyde, is a very special chemical. Formaldehyde-based resins are an incredibly effective and affordable option to use as glue in engineered wood for construction. It has strong performance in humid and high temperature variability environments and can insulate well. However, it’s also a volatile organic compound that hurts the respiratory system and is also a carcinogen at sufficient exposure. Consequently, many engineering companies are phasing formaldehyde out of their inventory.
Saturation Pressure
01/08/26
“What is the pressure at which a substance’s liquid and vapor phases are balanced with each other?”
Vapors form when molecules from a liquid bounce into the air as gases. At some pressures, more molecules escape, and at others, more return. The pressure where the molecular exchange between each phase is equal is known as the Saturation Pressure. The saturation pressure is dependent on temperature, since higher temperatures mean more molecules escape, necessitating a higher pressure to keep them contained. Saturation pressure dictates what the vapor makeup of a mixture will appear according to Raoult’s law.
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