Determining: Stack testing of sources (normal operating condition)

Transcription

1 class-notes-ch4_ , Page 1 of 8 4. EMISSION SUMMARIES 4.1 EMISSION FACTORS 4.2 EMISSION REPORTING 4. RISK ASSESSMENT 4.1 EMISSION FACTORS Definition: a representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with that pollutant. ER E = A EF (1 ) 100 ER = emission reduction (%) EF = emission factor (mass / activity unit) A = activity rate (activity unit / time) e. g. mass input / year energy input / year Uses: Estimating emissions for: C&A application Emissions reporting Regional modeling Estimating effect of APC devices Screening sources Determining: Stack testing of sources (normal operating condition) Quality: quality of source testing is assessed (standard Methodology, documentation) A, B, C or D test quality is derated (number of tests, variability, representation as average) A, B, C, D or E quality influences use:

2 class-notes-ch4_ , Page 2 of 8 Source: Procedures for Preparing Emission Factor Documents (EPA- 454/R , Revised) (USEPA, 1997) Keep in mind: A good emission factor is better than a poor source test! Cautions: these are averages (standard are not set at average; could be ½ over, ½ under) typical data only available for limited number of pollutants: CO, NOx, SO 2, PM, total VOCs most suitable for steady-state operations

3 class-notes-ch4_ , Page of 8 Sample Calculation: What is the SO 2 production from a 1000MW electric power plant using a wet-bottom, pulverized coal-fired furnace equipped with a wet scrubber to remove 98% of the SO 2 from the exhaust gases. Assume bituminous coal {10,500 14,000 BTU/lb, 2.1% S (by mass)} a) by mass balance coal burn rate: MW( BTU / h / MW) 0.456kg / lb = 40,420kg / h 12,000BTU / lb (0.) η =40Mg coal/h SO 2 conversion: (S+O 2 SO 2 ) 2.1Mg S 64Mg SO Mg SO2 ( 2 ) = Mg coal 2Mg S 042 Mg coal SO 2 production: 40Mg coal Mg SO2 (0.042 )(1 0.98) = 0.6Mg SO2 / h h Mg coal = 0.6 tonnes SO 2 /h b) by emission factor: AP-42, Table 1.1- ( wall-fired, pre NSPS, tangentially fired, NSPS; EF = 8S; quality A SO 2 production: 8(2.1) lb / ton(40mg 2000lb / ton coal / h) (1 0.98) = 0.4Mg SO 2 / h should always be less than mass balance calculation. References: USEPA (1999) Introduction to emission Factors [online].

4 class-notes-ch4_ , Page 4 of EMISSION REPORTING NPRI = National Pollutant Release Inventory a database of estimated toxic emissions from stationary sources in Canada facilities required to report must meet all of the following criteria: - more than 10 employees (or 20,000 worker hours/y) - manufacture, process or use > 10,000 kg per year of an NPRI substance at a concentration > 1% by weight exceptions: - some facilities excluded (eg. universities, gas stations, garages, research facilities) - some facilities not excluded (e.g. incinerators, chlorinated solvent manufactures, smelting) - small quantity/concentration exemption lower for some compounds (Hg > 5kg; 17 PAHs > 50kg; dioxins/furans and Hexachlorobenzene (HCB): certain facilities must report) NPRI list based on: - US Toxic Release Inventory List - Canada s Priority Substance List - Canadian Environmental Protection Act Toxics List Substances can be added to (2 for 2000) or removed from (1 acetone) the list Uses: - Setting environmental policies, priorities - Data for negotiation - Public right-to-know - Data for modeling Data search: Data available on the web ( Search by city, company, compound, postal code Third parties analyses data: Citizen s Environmental Alliance PollutionWatch

5 class-notes-ch4_ , Page 5 of 8 References: Guide for Reporting to the National Pollutant Release Inventory 2001, 2002 [online] O.Reg 127 (May1, 2001) Airborne discharge of 58 contaminants Includes NPRI discharges, greenhouse gases, PM Annual reporting for most compounds Quarterly reports from emission monitoring for NOx, SOx from electricity producers Reference: Ontario Ministry of the Environment A citizens guide to airborne contaminant reporting in Ontario (2002) Step by Step Guideline for Emission Calculation, Record Keeping and Reporting for Airborne Contaminant Discharge 4099e02 (2004) 4. RISK ASSESSMENT Definitions: Risk Assessment: an activity that estimates the frequency and spectrum of accidents and other negative events Risk Management: the use of quantitative knowledge of risks to make policy decisions What is risk? The likelihood or probability of a hazard causing an injury Policies must balance risk with benefit. Occupational: health risk vs. wages (voluntary) Environmental: health risk vs.? (involuntary) - Set standard to minimize additional risk

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7 class-notes-ch4_ , Page 6 of 8 Risk analysis is applied to carcinogens. Assumptions: 1) presence of carcinogen creates risk 2) risk increases linearly with dose ) time over which dose is distributed does not matter (one-hit model) P( d) = 1 exp( q0 q1d ) where P(d) = lifetime risk (probability of cancer) due to exposure d = dose or intake mg/(kg d) q 0, q 1 = parameters fit to data (q 0 corresponds to P(0)) Taylor series expansion: 2 x exp( x ) = 1+ x ! P(d) = 1 [1 + ( q use only these terms for small x (<0.01) 0 q d)] = q 1 P(0) = 1 [1 + ( q0)] = q0 Additional cancer risk: P( d) P(0) = q0 + q1d q0 = q1d intake slope factor - Apply to: low doses, affect linear with dose 0 + q 1 d Cancer Potency Slope, inhalation (CPSi) can be found on the USEPA s Integrated Risk Information System (IRIS) ( CA IR ET EF ED CDI = BW AT CDI = Chronic Daily Intake (mg/kg body weight d) CA = concentration in air (mg/m ) IR = inhalation rate (m /h), adult 20m /d, child 5m /d ET = exposure time (h/d) EF = exposure frequency (d/y) ED = exposure duration (y) BW = body weight (kg)

8 class-notes-ch4_ , Page 7 of 8 AT = average time (d) Example: What is an individual s additional risk of cancer if exposed to chloroform at the AAQC of 500 µg/m for their lifetime? CPSi = 0.08 (mg/kg d) -1 (500µ g / m )(10 mg / µ g)(20m / d)(65d / y)(70y) CDI = 70kg(65d / y)(70y) = (0.286m / kg d)(0.500mg / m rest in CDI eq. CA final unit: mg/ kg d P( d) P(0) = CPSi CDI = 0.08( mg / kg d) 2 1 (0.286m = (0.500mg / m ) Unit Risk Factor, units (mg/m ) -1 = ) / kg d)(0.500mg / m USEPA allows risks of 10-4 to 10-7 when setting standards. ) Total Risk = ΣRisk ij (risk from i chemicals by j pathways) NON-CARCINOGENS There is a no observed adverse effect level (NOAEL) The reference dose (RfD) or reference concentration (RfC) is calculated by applying a safety or uncertainty factor to the NOAEL. e.g. The lowest observed adverse effect level for chloroform administered orally to dogs was 1 mg/kg d. The RfD was set at NOAEL 1 uncertaint y factor = = = 100 RfD 0.01 factor of 10 for species conversion factor of 10 to protect sensitive human populations factor of 10 because LOAEL used instead of NOAEL

9 class-notes-ch4_ , Page 8 of 8 RfD for human is thus: 1 mg/(kg d) /100= 0.01 mg/(kg d) Q: What is the lifetime risk of cancer from drinking water containing chloroform at the RfD of 0.01 mg/kg d P( d) P(0) = CPSo RfD = ( mg / kg d) = (0.01mg / kg d) FINAL THOUGHT Thousands new chemicals on the market every year, detailed knowledge of all chemicals is lacking

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