guiding q's : poisons in nature, naturally occurring radiation

sources of natural poisons

• Animals: snakes (cobra, ciper, rattlesnake, coral snake), scorpions, spiders (black widow, brown recluse), and marine species (stingrays, scorpionfish, pufferfish)

• Plants: poison ivy (skin irritation), castor bean plant (ricin, deadly toxin)

• Algae: Dinoflagellates produce marine toxins that bioaccumulate in shellfish and fish → paralytic shellfish poisoning or ciguatera 

• Fungi: molds and mushrooms 

  • Ergot (on rye) and Aspergillus Flavus (on peanuts/corn) produce dangerous mycotoxins 

  • Amanita phalloides (“death cap”) mushrooms cause most global deaths from mushroom poisoning

ergot (claviceps purpurea)

• fungal parasite on rye and cereal grains

• produces alkaloid toxins causing vasoconstriction → loss of blood flow, gangrene, and convulsions (“St. Anthony’s Fire”)

Aflatoxins (Aspergillus flavus0

• grows on stored crops (especially peanuts and corn)

• causes acute liver toxicity and is a carcinogen (linked to hepatocellular carcinoma) 

• risk is greatest when combined w hepatitis B infection → ~60x greater cancer risk

ionizing radiation

• high-energy radiation that knocks electrons out of orbit, forming ions 

  • Ex’s: alpha particles, beta particles, gamma rays, X-rays, cosmic rays, and short wavelength UV-C

non-ionizing radiation

• lower energy; does not ionize atoms, but can still cause biological damage 

  • Ex’s: UV-A and UV-B, visible light, infrared, microwaves, radio waves

metrics used in assessing exposure to ionizing radiation

• Gray (Gy): measures energy absorbed per gram of tissue 

• Sievert (Sv): adjusts Gy by the biologica effectiveness of the radiation (accounts for how damaging it is)

  • Dose (Sv) = Dose (Gy) x Relative Biological Effectiveness (RBE)

  • RBE: Alpha ≈ 10 x Gamma, Beta ≈ 5 x Gamma 

• Becquerel (Bq): Measures radioactivity (1 disintegration per second)

• Older units: rad= 0.01 Gy; rem=0.01 Sv

key natural sources of exposure to radiation

• radon gas

• cosmic radiation 

• terrestrial radiation 

• internal exposure 

radon gas

•  #1 natural source of radiation exposure 

  • From uranium decay in soil/rock → inhaled in homes and mines

cosmic radiation

• from space

• exposure increases w altitude 

  • ex: higher in denver

terrestrial radiation

• comes from uranium and thorium in soil, rocks, and building materials

internal exposure to radiation

from food/water (plants absorb radioactive elements, animals eat plants)

radioactive decay

• Process by which unstable isotope (like uranium-238) release particles/energy to become stable 

  • Alpha decay: emits 2 protons + 2 neutrons (reduces atomic mass by 4) 

  • Beta decay: converts a neutron into a proton + electron (atomic number increases by 1)

  • Each isotope has a characteristic half-life (time for half to decay)

electromagnetic spectrum

• full range of radiation types organized by wavelength and energy 

  • Short wavelengths → higher energy (gamma, X-rays)

  • Long wavelengths → lower energy (radio, microwaves)

• All radiation travels at the speed of light 

  • Wavelength determines energy level and biological effect

High level exposure (≥1 Sv) to radiation 

• Causes radiation sickness: death of rapidly dividing cells (gut, bone marrow, CNS)

• Symptoms: nausea, vomiting, hemorrhage, anemia, immune failure, often fatal (≥ 2.5-5 Sv)

Low-level chronic exposure (mSv) to radiation 

• Causes DNA damage, increasing long term cancer risk 

• In utero: may cause miscarriage, malformations, or lowered IQ

human health risks of ionizing radiation

• Cancer: leukemia, thyroid, breast, lung, bladder, liver, colon, and skin (melanoma and nonmelanoma) 

• Developmental effects: fetal malformation, miscarriage, reduced IQ

human health risks of nonionizing radiation

• Skin cancer (UV-A/UV-B), cataracts, and immune suppression 

• But UV also triggers vitamin D synthesis, essential for bone health

Describe the electromagnetic spectrum and relate it to the distinction between ionizing and nonionizing radiation

• Dividing line lies in the ultraviolet range 

  • UV-C, X-rays, gamma rays → ionizing (enough energy to remove electrons)

  • UV-A/b, visible light, infrared, microwaves, radio waves → nonionizing (lower energy; heats or excites molecules but doesn’t ionize)

human health risks of radiation

• High dose exposure: acute radiation syndrome (fatal cell death)

• Chronic low dose: cumulative DNA mutations → cancer (no safe threshold)

• Natural exposure risks 

  • Radon gas: leading natural source of lung cancer after smoking 

  • UV exposure: causes basal cell, squamous cell, and malignant melanoma; also cataracts

  • In utero exposure: miscarriage, congenital defects 

• Protective aspect; moderate UV exposure enables vitamin D production