Chemicals, Drinking Water, Risk and Regulation

Transcription

1 Chemicals, Drinking Water, Risk and Regulation Brian G. Bearden, P.E. Mariana Islands Water Operators Association February 5, 2014 NPR Story: The Big Impact Of A Little-Known Chemical In W.Va. Spill Key Topics: The numbers of chemicals in use today How are they regulated? How does a chem. get chosen for an MCL? What goes into an MCL? What do we do when there is no MCL? Chemicals in Commerce Today CAS Registry: >80 million organic and inorganic substances (view latest numbers): EPA s TSCA Inventory All chemicals manufactured or produced in USA More than 84,000 *Excludes pesticides, drugs, food additives, cosmetics, munitions, and nuclear materials Chemical Regulation in the U.S. TSCA the Toxic Substances Control Act (1976) Despite 40 years of regulatory effort, chemical regulation in the United States has been a dismal failure, and our current law the Toxic Substances Control Act (TSCA) deserves much of the blame for this regulatory dysfunction. (Center for Progressive Reform, 2013) Instructor Bearden 1

2 TSCA Reform TSCA requires EPA to prove chemical s risk before it can impose testing requirements Since 1976, only 5 chemicals banned Proposals to replace TSCA have been discussed on and off for years Most recent, summer 2013 Lautenberg-Vitter Bill Chemicals and the SDWA National Primary Drinking Water Standards: the Maximum Contaminant Level (MCL) Currently 81 chemical contaminant MCLs selected as those which are thought to pose the most serious risk How are new MCLs added? The Candidate Contaminant List CCL : List Number of Year Number of Year contaminants proposed Regulatory Determinations CCL CCL CCL What is needed for an MCL? Determination of dose-response characteristics Toxicological (animal) testing Extrapolation to humans A Risk Assessment IRIS EPA s Integrated Risk Information System The IRIS Bottleneck U.S. Government Accountability Office (GAO) Report (2011) EPA very far behind its risk assessment goals Instructor Bearden 2

3 What is future for chemical regulation? Difficult to say look to Europe? REACH program requires chemical manufacturers to perform risk assessments, PRIOR to approval of chemical RISK ASSESSMENT & TOXICOLOGY a little more info The Concept of Risk: Technological advances in toxicology Image: Johns Hopkins University, Course Materials, EN Principles of Toxicology, Risk Assessment, and Management Prioritization of Chemicals Risk is a factor of exposure, as well as hazard Chemicals are prioritized for risk assessment as follows: Chemicals which are consumed by humans Foods and food additives High volume use chemicals Pesticides Solvents Industrial chemicals which can escape into the working area or environment Mercury Asbestos Toxicology Paracelsus: The Father of Toxicology Alle Ding' sind Gift, und nichts ohn' Gift; allein die Dosis macht, daß ein Ding kein Gift ist. All things are poison, and nothing is without poison; only the dose permits something not to be poisonous. The Dose Makes the Poison Source: Wikiedia, Paracelsus You are selling poison!!! ALL chemicals can be toxic, depending on dose: Water: LD 50 = 90,000 mg/kg (rat) 2013: Luana Priscyla Fernandes Soares, a 21-year-old Brazilian woman, died during a radio contest in Brazil, where her group drank 54 liters (14 gallons) of water mixed with Yerba Mate (a plant used in South American to make a tea-like beverage), an average of 5.4 liters/1.4 gallons per person. She collapsed one hour after the contest began. She suffered a stroke during the event and died two days later in the hospital. (Wikipedia Water Intoxication) Toxicity Testing Human data is preferred Epidemiological studies Accidents, spills Toxicity testing must be substituted in most cases Whole animal studies In vitro studies (cells and DNA) Botulinum toxin: LD 50 = mg/kg (human) Most toxic substance know to man Produced by bacterium Clostridium botulinum Instructor Bearden 3

4 Toxicity Testing Endpoints CARCENOGENCITY Mutagenicity Carcinogenicity NON-CARCINGENIC Acute toxicity Chronic toxicity Developmental toxicity Reproductive toxicity Dermal toxicity Occular toxicity Immunotoxicity Neurotoxicity Organ-specific toxicity Epidemiology Study of disease in human populations Can be very valuable if exposure is known NOT always the case Example: Arsenic in Taiwan Over 40,000 people drinking water exposure Enough data to allow determination of dose-response? Whole animal toxicity testing Hundreds of animals 3 to 5 years Millions of $ Provides very valuable data which in vitro testing cannot ent_image_landscape/images/colorbox/exposure.gif In vitro Testing Cells human and animal DNA Disadvantage: cells not animals New, rapid throughput assays can process thousands of samples in a short period of time, for fraction of cost of animal studies Can be combined with computer animal, human, and organ models to potentially replace animal testing in future Toxicity Test Results (noncarcinogen): rmal_12190.jpg MCL determined from No Adverse Effect Level (NOAEL) Image: Instructor Bearden 4

5 Toxicity Test Results (carcinogen): Non-carcinogen MCL: Toxicity test no adverse effects level is determined (NOAEL) Reference dose (RfD) determined by dividing by uncertainty factors: Divide by 10 for use of animal data Divide by 10 to account for human variability Etc. MCLG (MCL goal) determined by converting RfD to concentration and dividing by 5 (drinking water only 20% of exposure to chemical) MCL is set as close to MCLG as feasible, in consideration of other factors (treatability, cost, etc.) No safe level default assumption (not all agree) Image: Carcinogen MCL: MCLG is zero no safe exposure MCL set to practical quantitation limit (PQL) (Class A and B known or probable human carcinogens) For Class C (possible human carcinogens), MCLG is determined as for non-carcinogens, with additional safety factor of 10. Well, not really. Example: ARSENIC: ACUTE (high concentrations, short-term) Acutely toxic at high concentrations (60,000 µg/l causes death) Severe stomach and intestinal irritation (30,000 µg/l) Reproductive & teratogenic effects in animals at high concentrations CHRONIC (lower concentrations, long-term Skin pigmentation (black feet disease) Keratosis Skin cancer Class A carcinogen Evidence of lowered IQ in children Increased mortality in young adults Example continued: ARSENIC: EPA Oral RfD: Range: 0.1 to 0.8 mg/kg-day EPA scientists could not agree EPA MCLG: 0 ppm (carcinogen) EPA MCL: 0.01 ppm (0.01 mg/l or 10 μg/l) EPA considered range from 3 to 20 μg/l 50 μg/l previously 3 μg/l the technically feasible level Final decision based on: Cost benefit analysis MCL Cost-Benefit Analysis How Much is a Life Worth? EPA: $6.1 million Critics (CATO institute): $1.8 million Instructor Bearden 5

6 The MCL for Sausage When there is no MCL What can be done? Laws are like sausages, it is better not to see them being made. Otto von Bismarck Image: Associated Press Chemistry Quantitative Structure-Activity Relationships QSARs Can predict toxicity and environmental fate Based on chemical s structure MCHM 4-Methylcyclohexanemethanol OH Caffeine. Image: fyeahtattoos.com Chemical modeling software On the net: Very useful, very powerful provides software results from: EPA EPI Suite Chemicalize.org ACD/Labs Desktop: EPA EPI Suite Example: EPA EPI Suite EPI Suite does not contain MCHM can enter SMILES structure: CC1CCC(CC1)CO (from Wikipedia page) Or you can draw it (demonstration) Instructor Bearden 6

7 EPA s Results for Environmental Fate of MCHM: A moderate affinity for living tissue Moderately soluble Not volatile Low - moderate affinity for soil Biological degradation very probable Wastewater plant: 93% removal predicted Fugacity modeling (environmental fate): 66% to soil 33% to water Total persistence: 408 hours (17 days) Summarizing the NPR Story: Spill occurs No environmental or human health standards for MCHM This is not uncommon at all 85,000 chemicals in commerce in U.S. Chemical dangers & fate analyzed using: One existing animal test (lucky ) Computerized QSAR prediction models Chemical regulation in U.S. under fire Summarizing this presentation Over 8 million chemicals in commerce 85,000 chemicals regulated by TSCA 81 chemical standards under SDWA 105 chemicals on SDWA candidate contaminant list (CCL) EPA producing new risk assessments ~ 4 to 5 per year All chemicals pesticides, air pollutants, drinking water Developing an MCL a complex and lengthy process Not entirely based on science and safety Technological advances in the works that could speed up process Disclaimers: DO NOT PANIC! You are relatively safe Not all synthetic chemicals are harmful EPA does a good job of prioritizing chemicals for regulation Most other chemicals in environment are present at extremely low levels miniscule exposure rules out most risk Instructor Bearden 7