12 Chemical fact sheets - WHO

1 30712 Chemical fact sheetsThe background docu-ments referred to in this chapter (as the princi-pal reference for each fact sheet ) may be found on the Water, Sanitation, Hy-giene and Health web site at A complete list of r eferences cited in this chapter, including the background documents for each c hemical, is pro-vided in Annex Chemical contaminants in drinking-waterAcrylamide Residual acrylamide monomer occurs in polyacrylamide coagulants used in the treat-ment of drinking-water. In general, the maximum authorized dose of polymer is 1 mg/l.

2 At a monomer content of , this corresponds to a maximum theoretical concen-tration of g/l of the monomer in water. Practical concentrations may be lower by a factor of 2 3. This applies to the anionic and non-ionic polyacrylamides, but residual levels from cationic polyacrylamides may be higher. Polyacrylamides are also used as grouting agents in the construction of drinking-water reservoirs and wells. Human ex-posure is much greater from food than from drinking-water, owing to the formation of acrylamide in foods ( breads, fried and roasted foods) cooked at high temperatures.

3 Introduction(Chapter 1)A conceptual framework for implementing the Guidelines (Chapter 2)FRAMEWORK FOR SAFE DRINKING-WATERH ealth-based targets(Chapter 3)Public health context and health outcomeWater safety plans(Chapter 4)SystemassessmentMonitoringManagement and communicationSurveillance(Chapter 5)Application of the Guidelines in speci c circumstances(Chapter 6)Climate change, Emergencies, Rainwater harvesting, Desalinationsystems, Tr avellers, Planes and ships, INFORMATIONM icrobial aspects(Chapters 7 and 11) Chemical aspects(Chapters 8 and 12)Radiologicalaspects(Chapter 9)Acceptabilityaspects(Chapter 10)GUIDELINES FOR DRINKING-WATER QUALITY308 Guideline mg/l ( g/l)OccurrenceConcentrations up to a few micrograms per litre occasionally detected in tap waterBasis of guideline value derivationCombined mammary, thyroid and uterine tumours observed in female rats in a drinking-water study, and using the linearized multistage modelLimit of g/l by gas chromatography (GC); g/l by high-performance liquid chromatography (HPLC).

4 10 g/l by HPLC with ultraviolet (UV) detection Treatment performanceConventional treatment processes do not remove acrylamide. Acrylamide concentrations in drinking-water are usually controlled by limiting either the acrylamide content of polyacrylamide flocculants or the dose used, or both. Advances in analytical techniques are also beginning to allow control by direct measurement (see background document).Additional commentsEvery effort should be made to limit free acrylamide monomer in polyacrylamide used for water treatment, and water suppliers should also make every effort to ensure that residual acrylamide in drinking-water is kept as low as is technically feasible.

5 In particular, if acrylamide is controlled by limiting the amount dosed, overdosing should always be date2011 Principal referencesFAO/WHO (2011) Evaluation of certain contaminants in foodWHO (2011) Acrylamide in drinking-waterFollowing ingestion, acrylamide is readily absorbed from the gastrointestinal tract and widely distributed in body fluids. Acrylamide can cross the placenta. It is neuro-toxic, affects germ cells and impairs reproductive function. In mutagenicity assays, acrylamide was negative in the Ames test but induced gene mutations in mammalian cells and chromosomal aberrations in vitro and in vivo.

6 In a long-term carcinogenicity study in rats exposed via drinking-water, acrylamide induced scrotal, thyroid and adrenal tumours in males and mammary, thyroid and uterine tumours in females. The International Agency for Research on Cancer (IARC) has placed acrylamide in Group 2A (probably carcinogenic to humans). The Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) has recently noted concerns regarding the carcinogenicity and neurotoxicity of acrylamide and concluded that dietary exposure should be re-duced to as low a level as technically achievable.

7 Recent data have shown that expos-ure to acrylamide from cooked food is much higher than previously thought. As it is difficult to control the intake of acrylamide from food, it is very important that the acrylamide content of polyacrylamide used as a coagulant aid in water treatment, the most important source of drinking-water contamination by acrylamide, be as low as possible and that polyacrylamide not be overdosed in an attempt to take a shortcut to improving Alachlor ( Chemical Abstracts Service [CAS] No. 15972-60-8) is a pre-emergence and post-emergence herbicide used to control annual grasses and many broad-leaved weeds 30912.

8 Chemical fact SHEETSin maize and a number of other crops. It is lost from soil mainly through v olatilization, photodegradation and biodegradation. Many alachlor degradation products have been identified in soil. Alachlor was included in the Prior Informed Consent proced-ure of the Rotterdam Convention on the basis of the final regulatory actions taken by the European Community and by Canada to ban alachlor as a p esticide. Guideline mg/l (20 g/l)OccurrenceHas been detected in groundwater and surface water; has also been detected in drinking-water at levels below mg/lBasis of guideline value derivationCalculated by applying the linearized multistage model to data on the incidence of nasal tumours in ratsLimit of g/l by gas liquid chromatography with electrolytic conductivity detection in the nitrogen mode or by capillary column GC with a nitrogen phosphorus detectorTreatment mg/l should be achievable using granular activated carbon (GAC)Assessment date1993 Principal referenceWHO (2003)

9 Alachlor in drinking-waterOn the basis of available experimental data, evidence for the genotoxicity of ala-chlor is considered to be equivocal. However, a metabolite of alachlor, 2,6-diethylanil-ine, has been shown to be mutagenic. Available data from two studies in rats clearly indicate that alachlor is carcinogenic, causing benign and malignant tumours of the nasal turbinate, malignant stomach tumours and benign thyroid (CAS No. 116-06-3) is a systemic pesticide used to control nematodes in soil and insects and mites on a variety of crops. It is very soluble in water and highly mo-bile in soil.

10 It degrades mainly by biodegradation and hydrolysis, persisting for weeks to months. Guideline mg/l (10 g/l)OccurrenceFrequently found as a contaminant in groundwater in the vicinity of application areas, particularly when associated with sandy soil; concen-trations in well water as high as 500 g/l have been measured; aldicarb sulfoxide and aldicarb sulfone residues are found in an approximately 1:1 ratio in groundwaterAcceptable daily intake (ADI)0 mg/kg body weight based on cholinesterase depression in a single oral dose study in human volunteersLimit of mg/l by reversed-phase HPLC with fluorescence detectionTreatment mg/l should be achievable using GAC or ozonation Guideline value derivationallocation to water weight consumption 10% of upper limit of ADI60 kg adult2 litres/dayGUIDELINES FOR DRINKING-WATER QUALITY310 Additional commentsThe guideline value derived from the 1992 assessment of the Joint FAO/WHO Meeting on Pesticide Residues (JMPR)