Stage 1 and Stage 2 Microbial Disinfectants & Disinfection Byproducts

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Drinking Water Rules
Stage 1 and Stage 2 Microbial Disinfectants and
Disinfection Byproducts (M-DBP) Rules

After the amendments to the SDWA in 1996, rules were developed to balance the risks between microbial pathogens and disinfection byproducts (DBPs). It is important to strengthen protection against microbial contaminants, especially Cryptosporidium, and at the same time, reduce potential health risks of DBPs.

Stage 1 DBP rule was developed to protect public health by limiting exposure to these disinfectant byproducts.

According to the EPA, toxicology studies have shown several DBPs to be carcinogenic in laboratory animals, while others appear to cause adverse reproductive or developmental effects in laboratory animals. Epidemiology studies have suggested an association between certain cancers, and exposure to chlorinated water. More than 200 million people consume water that has been disinfected.

At NRC we have streamlined our compliance testing to meet all regulations. Your sample will be handled in accordance with standard methods and we will help maintain your monitoring schedule.

For the EPA Quick Reference Guide to Stage I DBP Rule, visit:
http://www.epa.gov/safewater/mdbp/qrg_st1.pdf

Stage 1 Disinfectants and Disinfection Byproducts Rule

Disinfection Byproducts

Contaminant	MCLG(mg/L)	MCL (mg/L)	Potential Health Effects from Ingestion of Water	Sources of Contaminant in Drinking Water
Bromate	zero	0.010	Increased risk of cancer	Byproduct of drinking water disinfection
Chlorite	0.8	1.0	Anemia; infants & young children: nervous system effects	Byproduct of drinking water disinfection
Haloacetic acids (HAA5)	n/a	0.060	Increased risk of cancer	Byproduct of drinking water disinfection
Total Trihalomethanes (TTHMs)	none --------- n/a	0.10 --------- 0.080	Liver, kidney or central nervous system problems; increased risk of cancer	Byproduct of drinking water disinfection

Disinfectants

Contaminant	MCLG (mg/L)	MCL (mg/L)	Potential Health Effects from Ingestion of Water	Sources of Contaminant in Drinking Water
Chloramines (as Cl₂)	MRDLG=4	MRDL=4.0	Eye/nose irritation; stomach discomfort, anemia	Water additive used to control microbes
Chlorine (as Cl₂)	MRDLG=4	MRDL=4.0	Eye/nose irritation; stomach discomfort	Water additive used to control microbes
Chlorine dioxide (as ClO₂)	MRDLG=0.8	MRDL=0.8	Anemia; infants & young children: nervous system effects	Water additive used to control microbes

Stage 2 DBP Rule
This final rule builds incrementally upon the previous rule and targets systems with the greatest risk. Systems that deliver disinfected water are required to meet maximum contaminant levels as an average at each monitoring location. Each size system must follow a prescribed monitoring schedule. The EPA has projected that this rule will prevent approximately 280 bladder cancer cases per year. Of these cases, 26% are estimated to be fatal.

For additional information, see the EPA Quick reference guide for your system:

Schedule 1 systems http://www.epa.gov/OGWDW/disinfection/stage2/pdfs/qrg_stage_2_dbpr_qrg_sch1_final.pdf

Schedule 2 systems http://www.epa.gov/OGWDW/disinfection/stage2/pdfs/qrg_stage_2_dbpr_qrg_sch2_final.pdf

Schedule 3 systems http://www.epa.gov/OGWDW/disinfection/stage2/pdfs/qrg_stage_2_dbpr_qrg_sch3_final.pdf

Schedule 4 systems
http://www.epa.gov/OGWDW/disinfection/stage2/pdfs/qrg_stage_2_dbpr_qrg_sch4_final.pdf