Ca na dian Drinking Water Guide lines Development Process

Transcription

1 Drafted: August 1993 Approved: February 1995 Revised: April 1998 Approved: April 1999 Ca na dian Drinking Water Guide lines Development Process pre pared by the Fed eral-provincial Sub com mit tee on Drinking Water

2 Table of Contents 1. In tro duc tion Identification As sess ment a) Field Mon i toring Data b) Cri te ria Sum mary Prep a ra tion c) Cri te ria Sum mary Review Eval u a tion a) Cost-Benefit Anal y sis b) Con sul ta tion De ci sion-making and Approval An nounce ment and Pub li ca tion Re-evaluation Com mu ni ca tion An nex 1: Op er ating Rules for the Sub com mit tee on Drinking Water Terms of Ref er ence Mem ber ship Fi nan cial Re spon si bil ities Sec re tar iat Re spon si bil ities DWS Chair per son s (Vice-Chairperson s) Re spon si bil ities DWS Mem bers Responsibilities Li ai son Mem bers Re spon si bil ities An nex 2: Approach to the Derivation of Drinking Water Guide lines In tro duc tion Mi cro bi o log i cal Pa ram e ters Chem i cal/phys i cal Pa ram e ters Ra dio log i cal Pa ram e ters Ap pen dix A: Cri te ria for Clas si fi ca tion of Car ci no ge nic ity Ap pen dix B: Def i ni tions

3 1. Introduction The Guide lines for Ca na dian Drinking Water Quality, pub lished by Health Can ada, pro vide a com pre - hensive set of drinking wa ter qual ity guide lines that are sci en tif i cally de fen si ble. The Guide lines ad dress mi cro - bi o log i cal, chem i cal, phys i cal and ra dio log i cal pa ram e - ters relevant to drink ing water qual ity is sues in Can ada. In 1983, a working group un der the Federal- Provincial-Territorial Com mit tee on En vi ron men tal and Oc cu pa tional Health ( CEOH ) began up dat ing the 1978 edi tion of the Guide lines for Ca na dian Drinking Water Qual ity. In 1986, this work ing group was changed to a stand ing sub com mit tee, the Fed eral-provincial Sub com - mit tee on Drinking Water ( DWS ) (see Annex 1 for Operating Rules). Since then, DWS has been de vel op ing new, and re vis ing ex ist ing, drinking wa ter guide lines. Mem bers of DWS in clude representatives of fed eral and provincial 1 de part ments of health and en vi ron ment. The Sec re tar iat for DWS is pro vided by Health Can ada specifically, the Drinking Water Section of the Safe Environments Di rec tor ate (Healthy En vi ron ments and Con sumer Safety Branch). In May 1993, CEOH di rected DWS to doc u ment the pro cess it uses to develop these guide lines specifically, the steps of identification, as sess ment, evaluation, de ci sion-making and approval, an nounce ment and pub li ca tion and re-evaluation (see Fig ure 1) while stress ing the im por tance of com mu ni ca tion among DWS, CEOH and the pub lic at all stages of the pro cess. Through out the en tire guide line development pro - cess, DWS uses the cri te ria out lined in the pub li ca tion, Strategies for Pop u la tion Health Investing in the Health of Ca na di ans (pre pared by the Fed eral, Pro vin - cial and Territorial Ad vi sory Com mit tee on Pop u la tion Health for the Meeting of the Min is ters of Health, September 14-15, 1994). These cri te ria cover the is sues of na tional significance, im pact, com mon directions, ca pac ity, return on in vest ment and flex i bil ity. The following sec tions con tain a brief de scrip tion of the steps involved in de vel op ing a Ca na dian drink ing water guide line using a hy po thet i cal Sub stance X for illustrative pur poses. It must be stressed that the development of Ca na dian drink ing wa ter guide lines relies on a flexible pro cess that must ac com mo date the diverse needs of var i ous ju ris dic tions. Cer tain of the steps de scribed below may be modified or circumvented in or der to address the needs of the jurisdictions involved. 1. The term provinces ( provincial ) as used throughout this document should be taken to include territories ( territorial ). Figure 1 Canadian Drinking Water Guidelines Development Process 3

4 2. Identification In or der to be con sid ered for guide line de vel op - ment, the following ques tions re gard ing Sub stance X must be asked: Could ex po sure to the sub stance lead to adverse health ef fects? Is it fre quently de tected or could it be ex pected to be found in a large num ber of Ca na dian drink ing water sup plies? Is the level at which it is de tected, or could be expected to be de tected, of pos si ble health sig nif i cance? If the an swer to these ques tions is yes, Sub stance X would receive fur ther con sid er ation for guide line de vel - op ment. It should be noted, however, that the fo cus of DWS is on pa ram e ters of na tional significance ( i.e., substances that are of in ter est and con cern across the coun try and/or to mul ti ple ju ris dic tions). In de cid ing whether a need ex ists for a guide line, the DWS Sec re tar iat must es tab lish that con trol ling the sub stance in drink ing wa ter would have an impact ( i.e., does con trol of Sub stance X have clear po ten tial, based on sound re search ev i dence, to significantly improve pop u la tion health and re duce dis par i ties?). In or der to de ter mine im pact, the Sec re tar iat must de ter mine the availability of pub lished lit er a ture and na tional field mon i tor ing data on Sub stance X. Ju ris dic tions rep re - sented on DWS iden tify the avail abil ity of pro vin cial field mon i tor ing data on Sub stance X from ex ist ing, cur - rent or fu ture sam pling pro grams, as well as timelines for pro vid ing mon i tor ing data sum ma ries of this in for - ma tion. The prov inces also identify ad di tional in for ma - tion that may be needed (e.g., tox ic ity mea sure ments, cost information, eco nomic sta tis tics) to as sist in the assessment of the sub stance and pos si ble sub se quent guide line development pro cess. Im pact is verified through fur ther re search at the cri te ria sum mary prep a ra - tion and review stages. In set ting the Pri or ity List of sub stances to be re - viewed, the Sub com mit tee uses a mul ti ple rat ing sys tem based on frequency and con cen tra tion of de tec tion, health ef fects and pro fes sional judge ment. DWS mem - bers are asked to rate each sub stance, first by rat ing how fre quently it is de tected in drink ing water sup plies, and then by rat ing the con cen tra tion at which it is usu ally detected in pro vin cial drink ing wa ter sup plies. Based on the first two rat ings, DWS mem bers rate the sub stance, us ing their pro fes sional ex pe ri ence and knowl edge of water sys tems, within their ju ris dic tion. If no mon i tor ing data are avail able to rate the sub stance, it is rated us ing only their ex pe ri ence and knowl edge. The Sec re tar iat pro vides the health ef fects rating. Based on pre-health risk as sess ment or as sess ments from the U.S. En vi ron men tal Pro tec tion Agency (EPA) or World Health Or ga ni za tion (WHO), the Sec re tar iat rates each sub stance (or group of sub stances) against its po ten tial to cause adverse health ef fects. With a sum mary of both ex po sure (e.g., con cen tra - tion, frequency) and heath rat ings and pro vin cial data, DWS es tab lishes the Pri or ity List through a con sen sus pro cess. The Pri or ity List is lim ited to the six sub stances that have the most impact on drink ing wa ter qual ity and pub lic health. The list con tains the sub stances the Sub - com mit tee is cur rently eval u at ing, pri or ity sub stances awaiting as sign ment to an evaluator, and suggested sub - stances that may be given pri or ity at a later date. If Sub stance X meets the above cri te ria, it is placed on the DWS list of sub stances for as sess ment or re as - sess ment. The list con tain ing Sub stance X and other parameters that are un der review or sched uled for re view by DWS is also re pro duced in the Guide lines for Canadian Drinking Water Quality book let, pub lished once ev ery two or three years. DWS reviews the list ev ery fall, and then sub mits it to CEOH for approval. If CEOH agrees with DWS s rec om men da tion, fur ther as sess ment of Sub stance X pro ceeds. If CEOH dis agrees with DWS s rec om men da - tion, either the sub stance is dropped from the as sess ment list or more in for ma tion is col lected on the sub stance to better jus tify the ini tial rec om men da tion. At this stage, the Sec re tar iat also consults with its part ners in other ju ris dic tions. The Sec re tar iat has a long his tory of co or di nat ing its eval u a tions with sim i lar work be ing un der taken at Health Can ada, the U.S. EPA and/or WHO. For in stance, the Sec re tar iat is wait ing until the EPA con cludes its extensive re search on ar senic be fore re-assessing the current Ca na dian arsenic guide line. Sim i larly, the EPA deferred its eval u a tion on ura nium un til the Sec re tar iat fin ished its re search on this sub stance. Based on the in for ma tion gath ered from DWS mem bers and other ju ris dic tions, the Sec re tar iat es tab - lishes a sched ule for the review of Sub stance X. It submits this sched ule, along with sched ules of other sub stances, to CEOH for review, com ments and approval. 3. Assessment a) Field Monitoring Data Dur ing the as sess ment phase, the is sue of flex i bil ity (i.e., that the pro cess pro vides flex i bil ity for each ju ris - dic tion and stake holder to im ple ment the strategy in their own way ) is con sid ered. For ex am ple, ju ris dic - tions par tic u larly con cerned about Sub stance X may ini - ti ate mon i tor ing pro grams. These ad di tional monitoring data for Sub stance X are gen er ally sub mit ted to the 4

5 Sec re tar iat for con sid er ation when as sess ing Canadian ex po sure to the con tam i nant. This ap proach to ad di tional data col lec tion and shar ing meets the com mon directions cri te rion, in that it is con sis tent with the pop u la - tion health di rec tions and pri or i ties of pro vin cial/ ter ri to rial and fed eral gov ern ments. The flex i bil ity and com mon di rec tions cri te ria are also ap plied once a guide line has been es tab lished. For ex am ple, the prov inces have the flex i bil ity to choose how they want to in cor po rate and im ple ment the new guide line into their drink ing water qual ity man age ment sys tem. For the mi cro bi o log i cal pa ram e ters in the Guide lines, there are, for ex am ple, vary ing strategies amongst prov inces with re spect to the num ber of samples re quired and the length of time be fore cer tain ac tions are taken (pub lic warn ings, boil wa ter or ders, etc.). This flex i bil ity allows each prov ince the op por tu - nity to develop im ple men ta tion cri te ria that best ad dress the type of mi cro bi o log i cal prob lems that are most likely to be en coun tered in their ju ris dic tion. b) Criteria Summary Preparation A Sec re tar iat Eval u a tor verifies the avail abil ity of ad e quate tox i co log i cal and/or ep i de mi o log i cal data ( i.e., sub stan ti ated pub lished ar ti cles) with which to as sess Sub stance X properly. The Eval u a tor then ini ti atesa comprehensive lit er a ture and data search, crit i cally re - views the lit er a ture and avail able mon i tor ing data, and as sesses Sub stance X in ac cor dance with Health Canada s pub lished ap proach policy ( Approach to the Der i va tion of Drinking Water Guide lines see Annex 2). Sub stance X has not been found to be car ci no genic to hu mans, so its rec om mended drinking wa ter guide line is derived based on the ap pli ca tion of an un cer tainty fac - tor, to ac count for inter- and intraspecies vari a tion, to a no-observed-adverse-effect level observed in tox i co log i - cal studies in which rats ingested Sub stance X in drink - ing water daily for two years. (Dif fer ent pro ce dures would have been used had Sub stance X been classified as a prob a ble hu man car cin o gen, a mi cro-organism or a radioactive con tam i nant.) The Eval u a tor drafts a cri te ria sum mary on Sub - stance X, in cor po rat ing the avail able health risk as sess - ment in for ma tion on Sub stance X, over all en vi ron men tal exposure, the frac tion of its ex po sure attributed to drink - ing water, ex ist ing an a lyt i cal/treat ment tech niques and ca pa bil i ties, and the rec om mended guide line value. c) Criteria Summary Review The first review of the draft cri te ria sum mary is internal: the Eval u a tor de fends the clas si fi ca tion of Substance X and its pro posed guide line to a Se nior Eval - u a tor within the Drinking Water Sec tion of the Safe Environments Di rec tor ate. The cri te ria sum mary is then revised to re flect the ex pe ri ence of the Se nior Evaluator, who must be com pletely satisfied with the cri te ria sum - mary be fore it is forwarded for an ex ter nal review. The Eval u a tor then sends the draft cri te ria sum mary to three ex ter nal or third-party reviewers who have expert knowl edge of Sub stance X. These third-party re - viewers are from Ca na dian or Amer i can universities, the U.S. EPA Drinking Water Pro gram or a Mem ber State of WHO. These ex perts crit i cally review the cri te ria sum - mary in ac cor dance with the Ca na dian pub lished approach policy (see Annex 2) and re spond to questions set out in a guide for peer reviewers. Their review fo cus - ses on the scientific com po nent of the sum mary. This third-party review re quires fi nan cial re sources, as re - viewers are paid un der con tract. The writ ten com ments and any ad di tional in for ma - tion identified by the reviewers are reviewed by the Evaluator. The Eval u a tor then re vises the cri te ria sum - mary and sub mits it for a final in ter nal review. The draft cri te ria sum mary, re vised on the ba sis of the fi nal in ter nal review, is then sub mit ted to the Standards & Guide lines Rul ings Com mit tee of the Safe Environments Di rec tor ate. This com mit tee, com posed of se nior staff from all ap pro pri ate di vi sions within the Di rec tor ate and ad di tional ex perts from within the Healthy En vi ron ments and Con sumer Safety Branch, evaluates the doc u ment to en sure that it is sci en tif i cally sound and in keeping with Departmental (or Di rec tor ate) pol i cies on health risk as sess ment. Taking into con sid er - ation com ments from this com mit tee, the Eval u a tor pre - pares a re vised cri te ria sum mary for sub mis sion to DWS. The cri te ria sum mary and an executive brief are then distributed to DWS mem bers and to all mem bers of the par ent com mit tee for review. Pro vin cial reviews and as sess ments of the cri te ria sum mary vary from brief de - part men tal (in ter nal) reviews to de tailed eval u a tions by external agencies or non-governmental or ga ni za tions. Written com ments from DWS members are for warded to the Sec re tar iat for con sid er ation by the Eval u a tor. All com ments are ad dressed and doc u mented, and a re vised cri te ria sum mary is drafted and re dis trib uted to DWS mem bers. 5

6 4. Evaluation a) Cost-Benefit Analysis Once the health risks as so ci ated with the in ges tion of Sub stance X in drinking wa ter have been eval u ated by the ju ris dic tions rep re sented on DWS, the fea si bil ity of im ple ment ing the rec om mended guide line for Sub stance X in drinking wa ter is eval u ated. This pro cess involves con sid er ation of treat ment cost and socio-economic factors ( ca pac ity and return on investment ). Ju ris dic tions con cerned that their pop u la tions may be ex posed to drinking wa ter con tain ing Sub stance X at con cen tra tions ex ceed ing the pro posed risk-as sess mentderived guide line value may con duct risk man age ment as sess ments. These as sess ments may involve es ti mat ing the costs for wa ter treat ment plant improvements de - signed to re duce the con cen tra tion of Sub stance X in treated wa ter sup plies. The costs of con trol ling ex po sure to Sub stance X from sources other than drink ing wa ter may also be es ti mated in or der to confirm that wa ter treat ment is in fact the most cost-effective way of re duc - ing intake of Sub stance X. These costs may be weighed against the benefits of re duc ing ex po sure to Sub stance X via drinking water. For ex am ple, there may be di rect sav ings in health care costs that would oth er wise be in - curred from a specific health prob lem as so ci ated with Sub stance X. There may also be in di rect savings, which are the socio-economic benefits (e.g., sav ings in sick leave, work or pro duc tion) as so ci ated with con trol ling Sub stance X in drink ing wa ter. Any side benefits that are an out come of improved drinking wa ter treat ment to con trol Sub stance X (e.g., removal of other con tam i - nants, ex ten sion of the life of the wa ter distribution system) may also be con sid ered in a cost-benefit analysis of Sub stance X. These as sess ments are the re spon si bil ity of DWS mem bers; the level of de tail is left to their dis cre tion. b) Consultation Con sul ta tion is closely linked with com mu ni ca tion (sec tion 8). Di rect input from stake holders and fo cus groups en ables those di rectly af fected by the health risks as so ci ated with Sub stance X to par tic i pate in the risk man age ment pro cess. This max i mizes pub lic un der - stand ing of the risk man age ment de ci sion-making pro - cess and in creases the like li hood for pub lic ac cep tance of the gov ern ment s fi nal de ci sion for the con trol of Sub stance X. Con sul ta tion be gins when Sub stance X is first iden - tified in an nounce ments and pub li ca tions as being under eval u a tion by DWS. DWS mem bers may so licit in put at this point. Con sul ta tion be comes more struc - tured once the cri te ria sum mary for Sub stance X has been sub mit ted to DWS for eval u a tion. DWS mem bers then iden tify the level of con sul ta tion re quired and inform CEOH of its rec om men da tion. A na tional con sul ta tion on the pro posed guide line is held. Re gional or pro vin cial con sul ta tions may also be rec om mended, depending on re gional or pro vin cial con cerns. Each DWS mem ber is re spon si ble for con sul ta tion pro ce dures or meth ods used within his or her own ju ris dic tion. The fed eral DWS mem ber is re spon si ble for national focus groups fed eral de part ments and agen cies, in dus tries and man u fac tur ers, and na tional or ga ni za tions and as so ci a tions. DWS mem bers are re spon si ble for an nounc ing the con sul ta tion on Sub stance X to their cli ents and re - questing that in ter ested par ties sub mit their names to the Secretariat. At the same time, a con sul ta tion pack age on Sub stance X con tain ing the cri te ria sum mary, a treat - ment tech nol ogy doc u ment de scrib ing com monly used or avail able con trol meth ods, avail able cost and eco - nomic anal y sis syn op ses, and any other relevant in for - ma tion is drafted by the Sec re tar iat and reviewed by DWS. Con sul ta tion pack ages are mailed out by the Sec re - tar iat to those par ties who ask to par tic i pate and are posted to Health Can ada s website for a six-month consultation period. Af ter the review pe riod, DWS mem - bers and members of the Sec re tar iat sum ma rize the re - sponses they have received, and the Sec re tar iat pre pares, from ju ris dic tional sum ma ries, a brief sum mary of com - mon com ments. This na tional sum mary re port is re - viewed by all DWS mem bers, re vised by the Sec re tar iat and re dis trib uted to DWS and CEOH mem bers and con - sul ta tion par tic i pants. 5. Decision-Making and Approval A pack age con tain ing all the con sul ta tion pack age ma te ri als as well as the results of the con sul ta tion ( i.e., the sum mary of all re sults) is distributed to DWS members one month in advance of the DWS meet ing at which dis cus sions are to com mence on a rec om mended ap proach for con trol ling Sub stance X in drink ing wa ter. At the meet ing, DWS mem bers decide whether or not a guide line for Sub stance X is needed and formulate a rec om men da tion. This rec om men da tion is then for - warded to CEOH for en dorse ment. CEOH as sesses the rec om men da tion based on the in for ma tion con tained in the executive brief, the cost and eco nomic anal y sis syn - op ses, and the na tional con sul ta tion sum mary re port. If the rec om men da tion for a new drink ing wa ter guide line is approved by CEOH, it is re ported to the Con fer ence of Dep uty Min is ters of Health via its Pop u - la tion Health Ad vi sory Com mit tee. If the rec om men da - tion to es tab lish a guide line is re jected, the item is re turned to DWS with di rec tions as to what ad di tional in for ma tion is required. 6

7 6. Announcement and Publication Af ter ob tain ing CEOH s approval for a new guide - line, the Sec re tar iat pre pares a pub lic an nounce ment for the news media. This brief state ment on CEOH s de ci - sion con cern ing the pro posed drinking wa ter guide line for Sub stance X is made avail able to all DWS mem bers. Each DWS mem ber is re spon si ble for the re lease of this state ment within his or her own ju ris dic tion. As the new guide line has been approved by CEOH, the Sec re tar iat Eval u a tor makes all re quired re vi sions to the cri te ria sum mary in prep a ra tion for pub li ca tion in the Guide lines for Ca na dian Drinking Water Qual ity Sup porting Doc u men ta tion binder. The fi nal cri te ria sum mary is pub lished in both official lan guages within one year of CEOH s approval. The new guide line is in cluded in the sum mary ta ble of drink ing wa ter guide lines found in the Guide lines for Ca na dian Drinking Water Qual ity Sup porting Doc - u men ta tion binder and is posted on Health Can ada s website. This ta ble is up dated an nu ally, if re quired. The guide line is also in cluded in the Guide lines for Ca na dian Drinking Water Quality book let, up dated every two or three years. 8. Communication Com mu ni ca tion be tween DWS and CEOH mem - bers is es sen tial throughout the guide line development pro cess to en sure that pro posed guide lines are in line with cur rent pol i cies. Com mu ni ca tion begins with the an nual review of the DWS list by CEOH and ends with the fi nal approval of the rec om mended guide line by CEOH. A sum mary of DWS activities and meet ing minutes are posted on Health Can ada s website and made available to CEOH mem bers af ter ev ery DWS meet ing. In an ef fort to keep the pub lic in formed on the development of drinking wa ter guide lines, a public announcement following each DWS meet ing is made available to DWS mem bers for distribution to in ter ested par ties, and is posted on Health Can ada s website. These an nounce ments are the sum ma ries of DWS activities pre pared for CEOH. These sum ma ries do not pro vide specific guide line val ues, as early dis clo sure of a pro - posed value could hin der the approval of that guide line. Chal lenges to a new or ex ist ing guide line are man - aged through an es tab lished for mal pro cess. 7. Re-evaluation Re-evaluation of ex ist ing guide lines is an on go ing pro cess. The Sec re tar iat has the re spon si bil ity for iden ti - fy ing out dated guide lines each year when the DWS list of sub stances is es tab lished, but any DWS mem ber or in ter ested party may iden tify an out dated guide line. The availability of new re search, mon i tor ing data, an a lyt i cal meth od ol ogy or treat ment process may prompt a re-evaluation of an ex ist ing guide line. 7

8 An nex1 : Operating Rules for the Sub com mit tee on Drinking Water Terms of Reference The Sub com mit tee on Drinking Water ( DWS ) shall provide timely ad vice to the Fed eral-provincial- Territorial Com mit tee on En vi ron men tal and Oc cu pa - tional Health ( CEOH ) on all mat ters that can af fect the provision of whole some drinking water, with em pha sis on: col lect ing, col lat ing and eval u at ing na tional and in - ter na tional in for ma tion on con stit u ents of drink ing water and their po ten tial health ef fects; developing and rec om mend ing guide lines for po ta - ble wa ter qual ity based on health as sess ment, treat - ment costs and eco nomic analysis; reviewing and eval u at ing the adequacy of po ta ble water treat ment tech nol ogy and op er at ing pro ce - dures in treat ment plants; pro mot ing the ex change of in for ma tion on drink ing water is sues and pro mot ing co-operation with other organizations with re lated in ter ests; and iden ti fy ing re search needs and pro mot ing and en - cour ag ing re search on drinking wa ter is sues in Can ada. Membership 1. Mem bers shall be nom i nated by CEOH health rep - resentatives ac cord ing to the following pro to col: one mem ber from each of the fed eral and provincial 1 gov ern ments. Pro vin cial DWS mem bers should be rep re sented by the pro vin cial agencies re spon si - ble for es tab lish ing drinking wa ter qual ity pa ram e - ters, or have the au thor ity to speak and make de ci sions for that ju ris dic tion on drink ing wa ter qual ity. If a DWS mem ber cannot at tend a meeting, the DWS mem ber may nom i nate an al ter nate for backup and con ti nu ity at that specific meeting. 1. Province ( provincial ) is understood to include territory ( territorial ). 2. The Chair per son and Vice-Chairperson shall be elected from and by the mem bers to serve a term of 2 years. The Chair per son and Vice-Chairperson may be re-elected to serve a sec ond term but shall not serve more than two consecutive terms. 3. In or der to en sure DWS op er ates within the over all pri or i ties of CEOH, DWS shall be as signed, on a rotational ba sis, a CEOH Li ai son, who shall be responsible for pro vid ing a li ai son func tion be - tween CEOH and DWS. The CEOH Li ai son shall be appointed through CEOH. Financial Responsibilities 4. Sec re tar iat sup port for DWS shall be pro vided by Health Can ada. 5. Health Can ada shall be re spon si ble for trans por ta - tion costs for the DWS meet ings of the mem bers nom i nated pur su ant to para graph 1, to the limit of one person per prov ince. 6. Mem bers shall bear their own sub sis tence costs while at tend ing the DWS meet ing. 7. Ad di tional per sons from the prov inces may par tic i - pate in these meet ings, but all costs for these par tic i - pants shall be the re spon si bil ity of the pro vin cial governments. 8. It is ex pected that Health Canada will pay for meet - ing room costs and re fresh ment ser vices during the meet ing. All other hos pi tal ity is op tional in ac cor - dance with the policy of the host ju ris dic tion. 9. DWS is en ti tled to hold two meet ings per year the lo ca tion al ter nat ing be tween Ottawa and a prov ince with due con sid er ation of costs involved. Secretariat Responsibilities 10. The Sec re tar iat shall pro vide advance notification of all DWS meet ings to the CEOH Sec re tar iat. 11. The Sec re tar iat shall make avail able, to the CEOH Sec re tar iat, de ci sion or in for ma tion items, an nual re ports out lin ing achieve ments and sta tus of work in prog ress, and a list of sub stances for the com ing 8

9 year, for ap proval by CEOH. Copies shall be for - warded to the DWS Chair per son and the CEOH Li ai son. 12. The Sec re tar iat shall be re spon si ble for the de vel op - ment of risk as sess ments for sub stances under review or sched uled for review (e.g., gath er ing and evaluating data on the health ef fects as so ci ated with exposure to a sub stance and de vel op ing op tions to re duce any perceived risks), in clud ing pre par inga risk man age ment cri te ria sum mary and coordinating other sum mary re ports or syn op ses for pre sen ta tion to DWS mem bers. 13. The Sec re tar iat a. shall so licit the views of mem bers on the agenda for the forth com ing meeting, b. may re quest members to pre pare and sub mit back ground in for ma tion for agenda items at least 4 weeks prior to the meet ing, and c. may re quest members to com plete an In for ma - tion Ex change form (to be pro vided by the Secretariat) at least 4 weeks prior to the meet ing for dis tri bu tion to the mem bers. 14. The Sec re tar iat shall distribute the agenda and background in for ma tion to DWS mem bers approximately 4 weeks prior to the meet ing. 15. The Sec re tar iat shall sub mit, to the CEOH Secretariat, draft min utes of its meet ings within 30 days of the meeting hav ing taken place and fi nal bi lin - gual min utes of its meet ings within 60 days. The Sec re tar iat shall make avail able to DWS and CEOH a pub lic an nounce ment (sum mary) pre pared from the min utes and shall post it on Health Can ada s water qual ity website also within 60 days of the meet ing. DWS Chairperson s (Vice-Chairperson s) Responsibilities 16. The Chair per son (Vice-Chairperson) shall a. give di rec tion to the Sec re tar iat on the de tails of forth com ing meet ings, b. en sure DWS meet ings are run in an efficient and effective manner, and c. keep the CEOH Li ai son in formed of progress on an on go ing ba sis. 17. The Chair per son (Vice-Chairperson) may convene an in for mal meet ing of the Sec re tar iat and other DWS mem bers, as ap pro pri ate, im me di ately prior to the meet ing to review the agenda and to at tend to any last-minute de tails. DWS Members Responsibilities 18. DWS is re spon si ble for the risk man age ment of sub - stances (e.g., eval u a tion of the im pact of the health data, as well as as sess ment of the prac ti ca bil ity, cost and po ten tial benefits of a par tic u lar pro posed guide line in light of other health pro tec tion pri or i - ties in the ju ris dic tions) and derivation of guide lines that are both prac ti ca ble and protective of health. 19. DWS shall normally arrive at de ci sions, con clu - sions, stan dards, guide lines and pro ce dures by con - sen sus. In the event that it be comes nec es sary to vote, each pro vin cial ju ris dic tion rep re sented shall have one vote. The federal vote shall be held by Health Can ada. 20. Voting shall be by bal lot. A quo rum shall be attained if at least three-quarters of the el i gi ble jurisdictions vote (this in cludes negative votes, af fir - mative votes and ab sten tions). A mo tion shall be passed if at least two-thirds of those cast ing votes are affirmative votes. Rea sons for negative votes or ab sten tions shall be re corded. If ad e quate in for ma - tion or data are avail able and a mem ber pre fers to de fer the de ci sion or vote on an is sue for fur ther evaluation, the is sue may be de ferred once un til the next meet ing. A write-in vote ap prox i mately 2 months following the meet ing may be held, but it shall not be con sid ered a de fer ral. 21. When pos si ble, the lo cal DWS mem ber will at tend any CEOH meet ing held in that DWS mem ber s jurisdiction for as sist ing the CEOH Liaison and DWS Sec re tar iat in pre sen ta tion of items and responding to ques tions on DWS activities. Liaison Members Responsibilities 22. To improve com mu ni ca tion be tween DWS and CEOH or the Ca na dian Ad vi sory Coun cil on Plumbing ( CACP ). The Liaison will review all issues dis cussed by DWS from CEOH s or CACP s perspective, and will keep the lat ter groups up-to-date on DWS activities and re spon si bil i ties. 23. At, and in be tween, CEOH or CACP meet ings, the Li ai son will re port on is sues of in ter est to the group in ques tion. Up com ing CEOH and CACP is sues and pri or i ties of con cern to DWS should be noted and brought to the at ten tion of the Sec re tar iat and to other DWS mem bers in a timely man ner. 24. At CEOH meetings, the CEOH Liaison will present and re port on for mal Sub com mit tee is sues and activities. The DWS Sec re tar iat and lo cal DWS member, if pos si ble, will as sist in the pre sen ta tion. 9

10 An nex 2: Approach to the Derivation of Drinking Water Guide lines Introduction The process of developing drink ing water guide lines for mi cro bi o log i cal, chem i cal/phys i cal and ra dio log i cal pa ram e ters is based on risk man age ment con cepts and involves sev eral steps: i) identification, ii) as sess ment, iii) eval u a tion, iv) approval and v) an nounce ment and pub li ca tion of the guide lines. It is a flex i ble pro cess that must ac com mo date the diverse needs of various ju ris dic - tions ( i.e., pro vin cial, ter ri to rial and fed eral). Cer tain steps may be modified in or der to sat isfy the needs of the ju ris dic tions involved. The sec ond step in the drink ing water guide lines de - velopment pro cess involves the scientific as sess ment of the health risk as so ci ated with the in ges tion of drinking water con tain ing specific pa ram e ters. Health Canada is re spon si ble for pre par ing these health risk as sess ments, based on careful con sid er ation of the avail able scientific data, and for rec om mend ing guide line val ues for mi cro - bi o log i cal, chem i cal/phys i cal and ra dio log i cal pa ram e - ters in drinking water, ac cord ing to the dif fer ent prin ci ples and ap proaches out lined in the following sec tions. As pro vin cial and ter ri to rial gov ern ments are responsible for the pro vi sion of safe drink ing wa ter and the im ple men ta tion of drink ing water guide lines, mem bers of the Fed eral-provincial Sub com mit tee on Drinking Water are ac count able for the eval u a tion and approval steps of the drink ing wa ter guide lines de vel op - ment pro cess. Each rec om mended guide line value and its accompanying health risk as sess ment are eval u ated for their prac ti cal ity and im pacts. National con sul ta tions are car ried out by the Sec re tar iat; pro vin cial or re gional con sul ta tions may be car ried out by the prov inces and ter ri to ries. Through this con sen sus-based development pro cess, a guide line is es tab lished, and the as so ci ated health risk as sess ment is modified to cre ate a cri te ria sum mary that re flects the risk man age ment de ci sions involved in the guide line s development. Microbiological Parameters Introduction Pathogens that com monly oc cur in pol luted surface water in clude pro to zoa (e.g., Giardia, Cryptosporidium ), bac te ria (e.g., Sal mo nella, Shigella, Campylobacter, Yersinia, Legionella ) and en teric vi ruses (e.g., Norwalk vi rus, rotaviruses, hep a ti tis A and E vi ruses [ HAV / HEV ]). Only en teric vi ruses and bac te ria are found in con tam i nated groundwater. Gastrointestinal ill ness or di ar rhoea is the most com mon ill ness attributable to waterborne patho gens. Al though such ill ness is gen er ally con sid ered to be non-life threat en ing in nor mal, healthy adults, low mortality rates (3-5%) have been observed in sensitive subpopulations, in clud ing infants and the elderly. More se ri ous ill ness, in clud ing jaun dice, liver dam age and, potentially, death (0.6% mor tal ity), may be caused by other waterborne patho gens, such as HAV. Four pri mary fac tors in flu ence the risk of waterborne ill ness to hu man health: the con cen tra tion of the patho gen in the drinking water. the hu man in fec tious dose of the patho gen. An in - fec tious dose may be a sin gle vi rus par ti cle or Giardia cyst, whereas much higher doses of bac te - rial patho gens are usu ally re quired to yield an in fec tion. the vir u lence of the patho gen and the im mune sta tus of the host. To pro tect the health of the most sen si - tive individuals (and hence all individuals), it is as - sumed for risk as sess ment pur poses that in fec tion equals ill ness, al though in fec tion does not always lead to ill ness. the vol ume of wa ter in gested. Av er age daily intake is as sumed to be 1.5 L. Be tween 1974 and 1987, 32 waterborne out breaks of bac te rial or i gin (1133 cases) and 10 waterborne out - breaks of giardiasis (315 cases) were re ported in 10

11 Canada. Dur ing the same pe riod, five waterborne vi ral (Norwalk vi rus and HAV ) out breaks, as so ci ated with 229 cases, were re ported. Gastroenteritis of un known aetiology ac counts for most waterborne dis ease out - breaks (1587 cases as so ci ated with 15 out breaks over the pe riod), but ev i dence is ac cu mu lat ing that in many cases the aetiological agents are vi ruses. It is likely that these re ported out breaks rep re sent only a frac tion of the true num ber of out breaks of waterborne ill ness. In for ma - tion for the pe riod since 1987 has not yet been com piled, but sig nif i cant waterborne dis ease out breaks have oc curred. Derivation of Maximum Acceptable Concentrations (MACs ) 1 For some waterborne pathogens (e.g., cer tain viruses and pro to zoa), one in fec tious unit can yield ill - ness. To pro tect sen si tive subpopulations, there fore, it is gen er ally as sumed in risk as sess ment that in fec tion will re sult in ill ness. As a re sult, there is no tol er a ble con cen - tra tion of waterborne pathogens in drinking water. This es sen tially means that the rec om mended MAC for waterborne patho gens is zero (sim i lar to the ap proach used for chem i cal car cin o gens). Even though the de sired goal for pub lic health pro - tec tion is zero risk of ill ness from waterborne patho gens, this is rarely tech ni cally and eco nom i cally fea si ble. In - stead, ac cept able mi cro bial risks are derived and used in risk as sess ment. The U.S. Surface Wa ter Treat ment Rule ( SWTR ), for ex am ple, has set a risk of one in fec - tion (as sumed to re sult in one case of ill ness) per peo ple per year (a risk of 10!4 ) as a health goal for ex po sure to Giardia in treated drinking water. In or der to ap ply health pro tec tion goals to wa ter man age ment, it is nec es sary to de ter mine whether there are any patho gens pres ent in the wa ter supply. However, it is im prac ti cal to mon i tor wa ter for the pres ence of patho genic or gan isms, for sev eral rea sons. For some patho gens, meth ods for di rect de tec tion have not yet been developed. For oth ers, the di rect de tec tion meth ods available are dif fi cult, costly and time con sum ing, and re quire well-trained per son nel. Fur ther more, the ab sence of one patho gen does not nec es sar ily in di cate that all other patho gens are ab sent. For these rea sons, sur ro gates or in di ca tors that can warn of in ad e quate wa ter treat ment, and hence the pos si - ble presence of patho gens in the water, are usu ally mon i - tored for in stead of the ac tual patho gens. The ideal in di ca tor or gan ism would have the following char ac ter is tics: Pres ent only when the patho gen is present, and more nu mer ous than the pathogen 1. See Appendix B for definitions. Exclusively as so ci ated with fae cal wastes and there - fore ab sent from non-polluted wa ters In ca pa ble of growth in the en vi ron ment Sim i lar re sis tance to stress (e.g., sim i lar survival char ac ter is tics, sim i lar re sis tance to dis in fec tion) as the pathogen Easily and ac cu rately enu mer ated Fae cal coliform bac te ria, in par tic u lar Escherichia coli and to tal coliform bac te ria micro-organisms that are not nor mally patho genic themselves are usu ally used to in di cate the po ten tial presence of patho genic bac te ria. For this rea son, fae cal in di ca tor bac te ria must never be pres ent in treated wa ter. If they are de tected, steps should be taken im me di ately to rec tify the sit u a tion. While the ab sence of coliforms in di cates that en - teric bac te ria are prob a bly ab sent, it does not guarantee that en teric vi ruses and parasitic cysts are also ab sent. This is be cause the coliform bac te ria are not an ap pro - pri ate in di ca tor for waterborne vi ruses and pro to zoa. For in stance, vi ruses survive lon ger in water, are more re sis - tant to dis in fec tion, and are more infective than most bac te ria. For these rea sons, coliphages (which are viruses that in fect coliform bacteria) and bac te rial spores have been pro posed as in di ca tors for en teric vi ruses in drink ing water. The use of spores of sulphite-reducing clostridia (e.g., Clostridium perfringens ) as an in di ca tor of the pres ence of vi ruses and pro to zoan cysts has also been investigated. The use of in di ca tor or gan isms is only one means of guard ing against the presence of waterborne patho gens. Ad e quate treat ment of drinking wa ter to remove or in ac - tivate these patho gens is of ten the pri mary method used to en sure against their presence in drinking water. The U.S. SWTR re quires all pub lic wa ter sys tems us ing any surface water, or groundwater un der the in flu ence of sur - face wa ter, to dis in fect as well as pro vide fil tra tion un - less cer tain char ac ter is tics of the source wa ter and site-specific con di tions are met. Treat ment must achieve at least 99.9% and 99.99% removal and/or inactivation of Giardia and vi ruses, respectively, mea sured by com - pli ance with specified dis in fec tant re sid ual con cen tra - tions and con tact times. The type and effectiveness of the dis in fec tant to be used de pend on the type of patho - gen pres ent and the phys i cal char ac ter is tics of the wa ter be ing treated. As this method for en sur ing waterborne patho gens are not pres ent in drinking wa ter sup plies is based on the de gree of treat ment re quired to remove or inactivate vi ruses and pro to zoan cysts rather than de tec tion, it avoids all the prob lems as so ci ated with the an a lyt i cal meth ods. This ap proach for as sur ing patho gen-free water is used by the Fed eral-provincial Sub com mit tee on Drinking Water. 11

12 In general, then, the ap pli ca tion of ad e quate wa ter treat ment and the ab sence of in di ca tor or gan isms are the pri mary means used to safe guard against the pres ence of haz ard ous waterborne patho gens. Health risks as so ci ated with the use of dis in fec tants (in clud ing the risk from their by-products) to keep drink ing water mi crobi o log i cally safe must also be con sid ered. Chemical/Physical Parameters 1 Introduction Data on the ef fects of ex po sure to chem i cal agents are ob tained in tox i co log i cal stud ies in an i mal spe cies and oc ca sion ally in ep i de mi o log i cal stud ies of hu man pop u la tions. Ef fects vary de pend ing upon the dos age, route of ex po sure (e.g., in ges tion, in ha la tion or der mal), fre quency or du ra tion of ex po sure and the spe cies, sex and age of the ex posed pop u la tion. Ef fects of ex po sure to chem i cals are gen er ally classified in the following broad categories: organ-specific, neu ro log i cal/ be hav ioural, re pro duc tive, teratological and oncogenic / car ci no genic/ mutagenic. Ef fects may be brief or pro - longed, re vers ible or irreversible, im me di ate or de layed, sin gle or mul ti ple. The na ture, number, severity, in ci - dence and/or prev a lence of specific ef fects in a pop u la - tion gen er ally in crease with in creas ing dose; this is com monly re ferred to as the dose-response re la tion ship. For some types of toxic ef fects that re sult from ex - po sure to chem i cals, it is believed that there is a dose (or thresh old) below which adverse ef fects will not oc cur. For other types of toxic ef fects, there is as sumed to be some prob a bil ity of harm at any level of ex po sure ( i.e., no thresh old). At present, the lat ter as sump tion is gen er - ally con sid ered to be ap pro pri ate for carcinogenesis only. For some types of car cin o gens ( i.e., those that induce tu mours by par tic u lar mech a nisms, such as pro - mo tion), however, there may be a threshold dose below which tu mours will not oc cur. Un cer tainty ex ists in the scientific da ta base used to derive guide lines for max i mum ac cept able ex po sure to chem i cal sub stances. Contributing to this un cer tainty are in ad e quate data on the level, frequency and du ra tion of ex po sure; dif fer ences in sensitivity be tween spe cies and among individuals in the same spe cies; in ad e quate study de sign; po ten tial for interactive ef fects; and vari a tions in sta tis ti cal mod els for ex trap o la tion of re sponses ob - served at high doses to those ex pected at low doses. Every ef fort has been made to take these un cer tain ties into ac count in the ap proaches for de riv ing MACs for chem i cal pa ram e ters de scribed in this section and the sup port ing doc u ments. It should also be em pha sized that 1. This section is taken from the Derivation of Maximum Acceptable Concentrations and Aesthetic Objectives for Chemicals in Drinking Water, as published in Part I of the 1989 Guidelines for Canadian Drinking Water Quality Supporting Documentation. the ap pli ca tion of sound scientific judg ment on a case-by-case ba sis is fun da men tal to the ap proach for deriving guide lines out lined in this sec tion. Proba bil is tic meth ods can be used in the risk as sess - ment of drinking wa ter pa ram e ters (mi cro bi o log i cal, chem i cal/phys i cal and ra dio log i cal) in or der to char ac - ter ize the un cer tainty and vari abil ity in those as sess - ments and to pro vide more in for ma tion for de ci sions about drinking wa ter guide lines. Since proba bil is tic meth ods are still be ing eval u ated by Health Can ada, they are cur rently used to sup ple ment the ex ist ing de ter min is - tic (point es ti mate) ap proaches to the risk as sess ment of chem i cal pa ram e ters (de scribed in this sec tion) on a case-by-case ba sis. The in for ma tion that these meth ods provide about risk ranges for chem i cal pa ram e ters can allow point es ti mates of risk and ex po sure to be put into context. However, cau tion must be ex er cised in the in ter - pre ta tion of the re sults of proba bil is tic meth ods; their suc cess ful ap pli ca tion is de pend ent upon the avail abil ity and qual ity of the nec es sary data and the use of com plex anal y ses. Derivation of MACs Different ap proaches are adopted for the derivation of guide lines for com pounds con sid ered to be car ci no - genic and prob a bly car ci no genic, com pounds con sid ered to be pos si bly car ci no genic, and those con sid ered to be prob a bly not car ci no genic or for which data are in ad e - quate for eval u a tion. It is nec es sary, there fore, to clas sify chem i cals with re spect to their po ten tial car ci no ge nic ity into var i ous groups (as out lined in Ap pen dix A) on the ba sis of rig or ous ex am i na tion of the quantity, qual ity and nature of the re sults of avail able tox i co log i cal and ep i de mi o log i cal stud ies. Chem i cals classified as car ci - no genic of ten also in duce toxic ef fects other than ma lig - nant tu mours; for these sub stances, the guide line is derived on the ba sis of the ap proach that leads to the most strin gent value. Chemicals That Are Not Carcinogenic For chemicals classified as prob a bly not car ci no - genic to hu mans or for which data on car ci no ge nic ity are in ad e quate for eval u a tion (Groups IV and V in Ap pen dix A), the MAC is derived based on a tol er a ble daily intake ( TDI ) (for merly called the ac cept able daily in take, or ADI ) for organ-specific, neu ro log i cal/ be hav ioural, reproductive or teratological ef fects. Where pos si ble, the TDI is derived by di vi sion of the low est no-observed-adverse-effect level ( NOAEL ) for a re - sponse con sid ered to be bi o log i cally significant by an un cer tainty factor. Ideally, the NOAEL is derived from a life time in ges tion study or stud ies in the most sensitive subpopulation (e.g., teratological stud ies). Data from acute or short-term studies are rarely used in cal cu lat ing TDIs. The un cer tainty factor is derived on a case-bycase ba sis, though in gen eral a fac tor of 1 to 10 times is 12

13 used to ac count for each of the fol low ing el e ments of un cer tainty: intraspecies vari a tion, interspecies vari a - tion, na ture and se ver ity of ef fect, ad e quacy of study and use of a low est-observed-adverse-effect level ( LOAEL ) ver sus a NOAEL. An ad di tional fac tor of 1 to 5 times is in cor po rated where there is in for ma tion that in di catesa po ten tial for in ter ac tion with other chem i cals. If the chem i cal is an es sen tial nu tri ent at low con cen tra tions, the di etary re quire ment is also taken into con sid er ation. Derivation of the MAC is gen er ally based on an average daily intake of 1.5 L of drink ing wa ter by a 70-kg adult (De part ment of Na tional Health and Wel fare 1981). However, where ap pro pri ate, the MAC is derived based on intake in the most sen si tive subpopulation (e.g., pregnant women, chil dren). Hu man ex po sure from sources other than drink ing wa ter (e.g., air, food, con - sumer prod ucts) is taken into ac count by ap por tion inga per cent age of the TDI to drinking wa ter. Where pos si ble, data con cern ing the pro por tion of to tal intake nor mally in gested in drink ing wa ter (based on mean levels in food, air and treated mu nic i pal wa ter sup plies) or in takes es ti mated on the ba sis of con sid er ation of phys i cal/ chem i cal prop er ties are used in the cal cu la tions. Where such in for ma tion is unavailable, a value of 20% is used in the derivation of the MAC. Con tam i nants present in drinking wa ter may con - tribute to to tal intake not only by in ges tion, but also by in ha la tion or der mal ex po sure to wa ter during bath ing and other house hold activities. For some com pounds, in - take by these routes is es ti mated to be sim i lar to that by in ges tion. However, in most cases, avail able data are in - sufficient to en able es ti ma tion of ex po sure by in ha la tion and der mal ab sorp tion of con tam i nants pres ent in drink - ing wa ter. The 20% al lo ca tion of to tal daily intake to drink ing wa ter is believed to be gen er ous and should be sufficient to ac count for these ad di tional routes of intake. In some cases where the cal cu lated to tal daily in take from all sources is less than 50% of the TDI, al lo ca tion to drinking wa ter is based on con sid er ation of ad di tional fac tors, such as fea si bil ity. In no case, however, can the cal cu lated to tal daily intake from food, air and drink ing water (con tain ing levels at the MAC) ex ceed the TDI. Max i mum ac cept able con cen tra tions must be achievable by avail able treat ment meth ods and mea sur - able by ex ist ing an a lyt i cal tech niques. Where a MAC is less than levels con sid ered to be re li ably mea sur able or achievable, an in terim MAC ( IMAC ) is es tab lished, and improvement in meth ods of quantitation and/or treat ment is rec om mended. Chemicals That Are Carcinogenic As it is gen er ally ac cepted that carcinogenesis is a non-threshold phe nom e non, it is as sumed that there is a prob a bil ity of harm at any level of ex po sure to car ci no - genic chem i cals. Ideally, there fore, car cin o gens should be ab sent from drinking wa ter. How ever, the in cre men - tal risks as so ci ated with ex po sure to low lev els of these chem i cals in drink ing wa ter may be suf fi ciently small so as to be es sen tially neg li gi ble com pared with other risks com monly en coun tered in so ci ety. Quantitative risks as so ci ated with ex po sure to low levels of po ten tial car cin o gens are es ti mated by ex trap o - lation (usu ally over many orders of mag ni tude) of the dose-response re la tion ship observed at high doses in experimental stud ies (most often in an i mal spe cies) to the low dose range. There are a num ber of un cer tain ties involved in these math e mat i cal ex trap o la tions; the meth - ods used are, however, based on conservative as sump - tions and prob a bly tend to over es ti mate rather than un der es ti mate the risks. The ac tual risks at low lev els of exposure may, there fore, be lower than the es ti mated values by 1 to 2 or ders of mag ni tude. For chem i cals classified as car ci no genic to humans or prob a bly car ci no genic to hu mans (Groups I and II in Ap pen dix A), life time can cer risks are es ti mated using the robust lin ear ex trap o la tion model, ap plied to the tu mour types con sid ered to be most ap pro pri ate from a bi o log i cal perspective. Wher - ever pos si ble, in for ma tion on pharmacokinetics, me tab o - lism and mech a nisms of car ci no ge nic ity is in cor po rated into the model for risk es ti ma tion. To ac count for dif fer - ences in met a bolic rates be tween an i mals and hu mans,a surface area to body weight cor rec tion is ap plied, ex cept in those cases where it is not justified on the ba sis of available data on pharmacokinetics and me tab o lism. For many car ci no genic com pounds (sub stances classified in Groups I and II in Ap pen dix A), avail able treat ment tech nol ogy is in ad e quate to com pletely elim i - nate ex po sure from drink ing wa ter. In ad di tion, avail able an a lyt i cal meth ods may be in ad e quate for re li able de ter - mi na tion at ex tremely low lev els. There fore, MACs are set as close to zero as rea son ably prac ti ca ble, on the basis of con sid er ation of the following fac tors: The MAC must be achiev able by available wa ter treat ment meth ods at rea son able cost. Wherever pos si ble, the up per 95% confidence limit for the life time can cer risk as so ci ated with the MAC is less than 10!5 to 10!6, a range that is gen er ally considered to be es sen tially neg li gi ble. In cases where intake from sources other than drinking wa ter (e.g., food, air and con sumer prod ucts) is sig nif i - cant, the up per 95% confidence limit for the life - time can cer risk as so ci ated with the MAC is less than or equal to 10!6. The MAC must also be reliably mea sur able by available an a lyt i cal meth ods. 13