Indoor emissions. foams) > CH 2 =O; plasticizers, especially dialkyl phthalates. Especially a problem with mobile homes. - Regulations in Sweden

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1 CHEM/TOX 336 Lecture 9 Indoor Air Emissions Radioisotopes in the Environment Indoor emissions From synthetic materials (carpets, plywood, ureaformaldehyde foams) > CH 2 =O; plasticizers, especially dialkyl phthalates. Especially a problem with mobile homes. - Regulations in Sweden require complete ventilation (no recycling) in new office building for the first 6 months of occupancy R = butyl, octyl, 2-ethylhexyl From cooking and heating activities: NOx, CO, including woodstoves, car fumes from garages New car smell = mixture of VOCs, total c > 64 mg/m 3 (new buildings mg/m 3 ) including toluene and other alkylbenzenes, styrene, acetone, C 5 to C 12 alkanes (Chem. Eng. News, May 20, 2002, p. 45)

2 Radioisotopes in the environment Toxicological aspects of ionizing radiation Primary Source: International Commission on Radiological Protection (ICRP) Publication #60, 1990 Definitions: 1 Bq = 1 disintegration per second (irrespective of energy) 1 Ci = Bq Emission Identity Energy Range Range MeV in air in water α He < 10 cm < 0.1 mm β e up to 10 m several mm γ photon up to 100 m several cm x-ray photon up to 10 m up to 1 cm neutron neutron 0-10 up to 100 m up to 1 α emission = bare He nucleus, energetic but poorly penetrating β emission = high energy electron: penetration depends on energy: β from 3 H cannot penetrate skin β from 31 P requires about 1 cm of Plexiglas γ emission = high energy electromagnetic radiation: highly penetrating, requires lead shielding Notice that for α or β released inside the body, almost all the energy is absorbed: this is why radon is dangerous. Ionizing radiation means that ions are formed: e.g.: H 2 O + energy H + + OH + e - Water is the most important target molecule because it is most abundant in living tissue. Both OH - and e - can damage biological macromolecules and therefore tissues by non-specific mechanisms: reductions of reducible functional groups (e - ) and hydrogen abstraction from lipids (OH ) initiating peroxidation and causing membranes to become leaky.

3 Energetics Usual units for radioactive disintegration are MeV, where 1 MeV ~ 108 kj mol -1 the important concepts are dose and dose rate one nuclear disintegration can cause thousands of ionization events, because the energies of covalent bonds are in the hundreds of kj mol-1. Dose (D) = Absorbed energy: 1 Gray (Gy) = 1 J kg -1 An acute dose of about 4 Gy will cause death over the next several days to weeks (data from Japanese A-bomb victims). Because some forms of radiation (especially γ) are penetrating, the absorbed dose may be much less than the total energy released upon nuclear disintegration Radiation weighting factors (W R ) The extent of damage from radiation depends on both the absorbed dose and the type of radiation involved. Radiation type W R photons (γ and x-rays) 1 electrons (β rays) 1 neutrons 5-20 depending on energy* α particles 20 * most damaging near 1 MeV

4 Tissue weighting factor (W T ) For living tissue, a tissue weighting factor (W T ) takes account of the variation of biological sensitivity of different organs. Tissue W T Gonads 0.20 Bone marrow, colon, lung, stomach 0.12 each Bladder, breast, liver, esophagus, 0.05 each thyroid Skin, bone surface 0.01 each All others 0.05 Total = 1.00 W T apportions the whole body dose among the various organs. This would be appropriate for external radiation sources, but not for (e.g.) inhaled radon or iodine isotopes, which localize to specific tissues Effective Dose (E), J kg-1, has the special name Sievert (Sv). Effective dose = Σ(D W R W T ) summed over all tissues The effective dose is a function of: radiation intensity, Bq type of radiation energy of radiation, MeV how easily radiation is absorbed the tissue into which the energy is deposited

5 Ionizing radiation in the environment natural radioisotopes 40 K; 235 U; 238 U and daughters such as 222 Rn radioisotopes formed by cosmic rays 14 N + n > 14 C + p + Hence radiocarbon dating since t ½ = 5500 years medical x-rays fall-out from nuclear testing nuclear industry: see below Typical exposure to ionizing radiation = 1-2 msv/year mostly from cosmic radiation Hazards from radiation Stochastic effects = random with no threshold; depend on total dose, not on the dose rate Fatal Cancers (all): 0.05 Sv -1 (no signature cancers) Non-fatal cancers: 0.01 Sv -1 Hereditary effects: 0.01 Sv -1 background radiation for a 75 year life span ~ 75 yr 0.001/yr > Sv > fatal cancer probability ~ This is 0.4% of all mortalities; total cancer death rate=0.25 Radiation workers: ICRP recommendation for maximum lifetime exposure = 1 Sv > 20 msv yr -1 for a 50 year maximum working life for the maximally-exposed individual. lifetime fatal cancer risk: = 0.02 Sv yr yr 0.05 Sv - 1 = 0.05 annual fatal cancer risk: = 0.02 Sv yr Sv - 1 = yr -1

6 Compare these values: total fatal cancer risk of ~0.25 in North America manufacturing industry: risk of accidental death = 1 in 40,000 per year (Vennart, 1991); over 50 yr. General Public: maximum additional exposure <1 msv yr -1, adding another (maximum) to the lifetime fatal cancer risk (not distinguishable epidemiologically) Dilemmas implicit in the ICRP approach (all worst case scenarios) The standard to protect radiation workers adds an excess fatal cancer rate of 0.05, which is ~ 20% of the prevailing rate for the population at large. It is much higher than the risk of accidental death in industry. These standards are very different from those used to regulate chemical toxicants (e.g., the arbitrary standard of 10-6 extra fatal cancers per lifetime). So: Is the standard for regulating chemical carcinogens too strict? Or: Is the standard for regulating ionizing radiation too lax? The case of radon Radon: naturally-occurring noble gas formed through decay of natural uranium and thorium. Chief isotope of concern is 222 Rn, t ½ 3.8 d, α emitter, MeV. Energy per disintegration: = MeV ( J MeV -1 ) = J Bq -1 U.S. data indicate a quarterly limit of 18 µci of radon breathed (72 µci/yr): CRC Handbook of Chem. and Physics, 1993 ed.

7 Different countries have set "action levels" for radon (ICRP Publication 60, para 217). Estimated volume of air breathed: L day -1 = L yr -1 U.S. action level: 4 pci L -1 = 0.15 Bq L -1 = Bq yr -1 = 30 Ci yr-1 Canadian action level: 20 pci L -1 = 0.74 Bq L -1 = Bq yr -1 = 150 µci yr -1 Canadian effective dose rate: (α radiation has W R = 20): E = ( Bq) ( J) 20 1 yr 1 Bq = J yr -1 Assume 2 kg of lung tissue > Sv yr -1 > Sv for a 75 year lifetime > fatal cancer risk of

8 Problems: From: ACGIH TLV s and BEIs 2001 Adopted Threshold Limit Values Table: Substance [CAS No.] TWA STEL Notations MW TLV Basis Heptane [ ] 400ppm 500ppm Irritation; narcosis Acetone 500ppm 750ppm Irritation sec-butyl acetate 200ppm Irritation chromium Metal and Cr III cmpds 0.5mg/m3 - - Varies Irritation, dermatitis Water-soluble Cr VI cmpds 0.05mg/m3 - - Varies Liver, kidney, respiratory Insoluble Cr VI cmpds 0.01mg/m3 - - Varies Cancer, irritation copper Fume 0.2mg/m Irritation, GI Dusts as Cu 1mg/m3 - - diethylamine 5ppm 15ppm Irritation dimethylformamide 10ppm liver divinyl benzene 10ppm irritation lead 0.05mg/m CNS,blood,kidney, reproductive methyl ethyl ketone 200ppm 300ppm 72.1 Irritation, CNS p-nitrochlorobenzene 0.1ppm anoxia,bood,liver perfluoroisobutylene - C 0.01ppm irritation,pulmonary edema phosphine 0.3ppm 1ppm - 34 irritation,cns,gi phthalic anhydride 1ppm irritation sulfuric acid 1mg/m3 3mg/m irritation,cancer(larynx) terephthalic acid 10mg/m lung,urinary tin Metal 2mg/m stannosis Oxide and inorganic 2mg/m3 - - Varies stannosis Organic 0.1mg/m3 0.2mg/m3 - Varies CNS,Immunotoxicity irritation turpentine 100ppm irritation vinyl chloride 1ppm cancer(liver) xylene 100ppm 150ppm irritation

9 Determine if the air containing the following chemical species are considered safe in the workplace for a full day exposure: 400 ppm of acetone, 150 ppm of sec-butyl acetate and 100 ppm of methyl ethyl ketone 0.05 mg/m3 lead and 0.7 mg/m3 sulfuric acid 3 ppm dimethylformamide,.01 ppm p-nitrochlorobenzene, and.5 ppm vinyl chloride 33 ppm turpentine, 80 ppm xylene, and 1 ppm divinyl benzene. 0.1 mg/m3 chromium (III), 0.45 mg/m3 copper dust, 0.15 mg/m3 organotin 8 mg/m3 terephthalic acid and 0.8 ppm phthalic anhydride Which of the following situations would be considered unsafe in the workplace: 3 ten minute exposures to 0.8 ppm phosphine and 0.01 ppm for the rest of the day 1 two minute exposure to ppm of perfluoroisobutylene 1 ten minute exposure to 20 ppm of diethylamine and none for the rest of the day

Radiation Safety Information for Students in Courses given by the Nuclear Physics Group at KTH, Stockholm, Sweden

Radiation Safety Information for Students in Courses given by the Nuclear Physics Group at KTH, Stockholm, Sweden September 2006 The aim of this text is to explain some of the basic quantities and units