Environmental Science Toxicology and Human Health 2 — Questions and Answers
Question 1: Sick Building Syndrome (SBS) is primarily associated with:
- Bacterial contamination of water pipes in aging buildings
- Poor indoor air quality from inadequate ventilation, VOCs, mold, or chemical off-gassing (Correct answer)
- Electromagnetic radiation from computers and electrical equipment
- High indoor carbon dioxide levels from overcrowded spaces
Correct answer: Poor indoor air quality from inadequate ventilation, VOCs, mold, or chemical off-gassing
SBS describes acute health and comfort effects linked to time spent in a particular building, typically caused by poor ventilation, VOC emissions from building materials, mold, and other indoor air pollutants.
Sick Building Syndrome encompasses headaches, eye/nose/throat irritation, fatigue, dizziness, and difficulty concentrating linked to time spent in a specific building. Causes include: inadequate fresh air ventilation; volatile organic compounds (VOCs) off-gassing from carpets, paints, furniture, and cleaning products; biological contaminants (mold, bacteria, dust mites); and combustion byproducts. The EPA estimates indoor air can be 2-5x more polluted than outdoor air. Tight, energy-efficient buildings can trap pollutants if ventilation is insufficient.
Question 2: Radon gas is a public health concern in homes primarily because:
- It reacts with indoor humidity to form corrosive acids that damage lungs
- It is a naturally occurring radioactive gas that decays to radioactive particles lodged in lungs, causing lung cancer (Correct answer)
- It displaces oxygen in enclosed spaces, causing asphyxiation
- It is released by PVC plumbing pipes when in contact with hot water
Correct answer: It is a naturally occurring radioactive gas that decays to radioactive particles lodged in lungs, causing lung cancer
Radon (Rn-222) is a decay product of uranium in soil/rock; it seeps into buildings and its short-lived radioactive progeny (polonium isotopes) emit alpha particles when inhaled, damaging lung tissue.
Radon is a colorless, odorless, tasteless noble gas formed in the natural radioactive decay series of uranium-238. It seeps from soil and rock through foundations into buildings, accumulating in basements and lower floors. Radon decays rapidly to short-lived polonium, bismuth, and lead isotopes that attach to dust and lung tissue, emitting damaging alpha radiation. The EPA estimates radon causes ~21,000 lung cancer deaths per year in the U.S. (second to smoking). EPA action level: 4 picocuries per liter; mitigation uses sub-slab depressurization.
Question 3: The primary health effect associated with long-term exposure to asbestos fibers is:
- Kidney failure from fiber accumulation in renal tubules
- Lung diseases including asbestosis, mesothelioma, and lung cancer (Correct answer)
- Liver cancer from asbestos particles entering the bloodstream
- Skin cancer from surface contact with asbestos-containing materials
Correct answer: Lung diseases including asbestosis, mesothelioma, and lung cancer
Inhaled asbestos fibers lodge permanently in lung tissue; they cause asbestosis (fibrosis), mesothelioma (cancer of the pleural/peritoneal lining), and lung cancer - all with long latency periods (20-50 years).
Asbestos refers to several naturally occurring silicate mineral fibers (chrysotile, crocidolite, amosite) widely used in insulation, roofing, and construction until the 1970s-80s. Inhaled fibers cannot be cleared by macrophages and persist in lung tissue and pleura indefinitely. Asbestosis: diffuse pulmonary fibrosis. Mesothelioma: an aggressive cancer of the pleural or peritoneal mesothelium; latency 20-50 years; almost exclusively linked to asbestos. Lung cancer risk is multiplicatively increased when asbestos exposure is combined with smoking.
Question 4: The EPA's risk assessment process for carcinogens typically assumes:
- A threshold dose below which no cancer risk exists, as established by animal studies
- A linear no-threshold (LNT) model where any exposure carries some risk proportional to dose (Correct answer)
- Cancer risk only applies above the NOAEL established from epidemiological studies
- Carcinogens are safe below concentrations found in natural background environments
Correct answer: A linear no-threshold (LNT) model where any exposure carries some risk proportional to dose
For genotoxic carcinogens, U.S. EPA typically uses the linear no-threshold (LNT) model, assuming risk is proportional to dose with no completely safe exposure level, to be protective.
The linear no-threshold (LNT) model assumes that carcinogenic risk is proportional to dose and that there is no dose below which the risk is zero, based on the premise that a single DNA mutation could initiate cancer. It is used conservatively by U.S. EPA, NRC, and ICRP for radiation and genotoxic chemical carcinogens. Cancer slope factors derived from high-dose animal or epidemiological studies are extrapolated to low environmental doses to calculate acceptable exposure levels (e.g., 1-in-a-million excess lifetime cancer risk).
Question 5: Persistent Organic Pollutants (POPs) are regulated under the Stockholm Convention primarily because they:
- Decompose rapidly in warm tropical climates but persist in cold regions
- Resist degradation, bioaccumulate in fatty tissues, travel globally, and cause serious human and ecosystem harm (Correct answer)
- Are entirely synthetic chemicals not found in any natural environment
- Primarily affect freshwater ecosystems and have no impact on terrestrial food webs
Correct answer: Resist degradation, bioaccumulate in fatty tissues, travel globally, and cause serious human and ecosystem harm
POPs (DDT, PCBs, dioxins, furans, PBDEs, PFAS) share four properties: persistence (resist degradation), bioaccumulation (concentrate in fat), long-range transport (deposited globally via atmosphere/ocean), and toxicity.
The Stockholm Convention (2001, now 180+ parties) initially targeted 12 POPs (the dirty dozen): 8 pesticides (DDT, aldrin, dieldrin, endrin, chlordane, heptachlor, mirex, toxaphene), 2 industrial chemicals (PCBs, hexachlorobenzene), and 2 byproduct groups (dioxins/furans). The Convention has been amended to add dozens more including PBDEs, PFOS, and PFOA. POPs travel via the grasshopper effect - volatilizing in warm regions, condensing in cold regions - leading to Arctic contamination far from emission sources.
Question 6: The precautionary approach to chemical risk assessment, as applied in the EU's REACH regulation, requires:
- Companies to wait for epidemiological evidence of harm before restricting chemical use
- Manufacturers to demonstrate the safety of chemicals before marketing rather than waiting for evidence of harm (Correct answer)
- Chemicals to be tested only when they are produced in quantities exceeding 1,000 tonnes per year
- Government agencies to conduct all chemical safety testing using public funds
Correct answer: Manufacturers to demonstrate the safety of chemicals before marketing rather than waiting for evidence of harm
EU REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) places the burden of proof on industry to demonstrate safety, in contrast to the U.S. approach where regulators must prove harm before restricting a chemical.
The EU's REACH regulation (2006) requires manufacturers and importers to register chemicals, provide safety data, and demonstrate that risks are adequately controlled before placing them on the market. For substances of very high concern (SVHCs - carcinogens, mutagens, reproductive toxins, persistent/bioaccumulative/toxic substances), REACH requires authorization before use. This contrasts with the U.S. Toxic Substances Control Act (TSCA), where EPA must demonstrate a chemical poses unreasonable risk before restricting it.
Environmental Science Toxicology and Human Health 2
Sick Building Syndrome (SBS) is primarily associated with: