Volume 7 - 2005

This paper discusses current issues with drinking water disinfection by-products (DBPs),
which include emerging (unregulated) DBPs that can be formed at greater levels with
alternative disinfectants (as compared to chlorine) and routes of human exposure (which
include inhalation and dermal exposure studies, in addition to ingestion). Health effects
driving DBP research include the recently observed reproductive/developmental effects
(including spontaneous abortion) observed in epidemiologic studies, as well as the
discrepancy between the types of cancer observed in animal studies for regulated DBPs
(mostly liver cancer) and the types of cancer observed in human epidemiologic studies
(mostly bladder cancer). Emerging DBPs discussed in this paper include iodo-acids,
bromonitromethanes, iodo-trihalomethanes (THMs), brominated forms of MX, bromoamides,
a bromopyrrole, and nitrosodimethylamine (NDMA) and other nitrosamines. Recent toxicity
studies have revealed that several of these DBPs are more genotoxic (in isolated cells) than
many of the DBPs currently regulated, and new occurrence data have revealed that many of
these DBPs can, in some cases, be present at levels comparable to regulated DBPs. Of the
alternative disinfectants, chloramination appears to increase the formation of iodo-acids,
iodo-THMs, and NDMA and other nitrosamines, relative to chlorine. Preozonation appears to
increase the formation of halonitromethanes.

Chloroform and other bromochlorotrihalomethanes were first identified as disinfection
byproducts (DBPs) in chlorinated water in 1970s. Since then, many other DBPs have
been identified such as haloacetonitriles, haloacetaldehydes, cyanogen halides,
aldehydes, ketoacids, chlorite, bromate and other organic and inorganic compounds. Due
to their occurrence and potential health risks, the U.S.EPA promulgated the Stage I
Disinfectants and Disinfection Byproducts (D-DBP) Rule in 1998. To assist water utilities
monitoring DBPs in their finished water, the U.S. EPA published a list of approved
analytical methods under the D-DBP Rule. In 1996, the U.S. EPA also promulgated the
Information Collection Rule (ICR) to collect brackground information on DBPs and
pathogens for the Stage II D-DBP-Rule. Actually 500 DBPs are known but few have been
investigated for their quantitative occurrence and health effects. Due to the fact that their
identification and quantitation have become extremely important to drinking water
companies in order to reduce or remove their presence, other analytical methods different
from those proposed by U.S. EPA have been optimized and are now commented in this
article.

The formation of Disinfection By-Products (DBPs) in drinking water results from the
reaction of chlorine or other disinfectants added to the water with naturally occurring
organic materials, and has raised concerns during the last decades because these
compounds are harmful for human health. During the present work, the formation of
different categories of DBPs was investigated in four water treatment plants (WTP) using
chlorine as disinfectant, and in selected points of the distribution network of Athens,
Greece, which is supplied from these four WTP, during a period of ten years. The
concentrations of DBPs were generally low and the annual mean concentrations always
well below the regulatory limit of the European Union (EU) for the total trihalomethanes
(TTHMs). The haloacetic acids (HAAs) have not been regulated in the EU, but during this
investigation they often occurred in significant levels, sometimes exceeding the levels of
TTHMs, which highlights the importance of their monitoring in drinking water. Apart from
THMs and HAAs, several other DBPs species were detected at much lower
concentrations in the chlorinated waters: chloral hydrate, haloketones and, in a limited
number of cases, haloacetonitriles.

Chlorination disinfection by-products (DBPs) are formed when water is chlorinated and the
organic matter in the water reacts with chlorine to form these by-products. There have
been concerns about the potential health effects of these by-products, including cancer and
reproductive effects. Here we have reviewed the literature on reproductive health effects.
Epidemiological studies on neural tube defects, urinary tract defects and small for gestation
age/intra growth retardation have shown the most consistent statistically significant
associations with an index of DBPs, but generally the risk estimates are small. The
interpretation of the studies is not straight forward because they may not be directly
comparable because of differences in DBP mixtures, exposure categories and actually
uptake of DBPs due to differences in e.g. ingestion rates, showering, bathing, and
swimming. Only few specific DBPs have been studied and THMs have often been used as
a marker for other DBPs, since they are often routinely available. Sample sizes, and
therefore power, have at times been low, particularly when the population was split into
exposure categories. Although most studies considered some confounders, (residual)
confounding by other water contaminants or other factors related to water intake, cannot
always be excluded. Case ascertainment, for outcomes such as spontaneous abortion and
certain congenital anomalies is far from straight forward, and for the latter at times
anomalies are lumped together with different aetiology, which may be inappropriate.
Furthermore, as with many reproductive epidemiological, if the putative agent affects both
early pregnancy loss and later birth outcomes such as congenital anomalies, interpretation
of later birth outcomes may be more difficult.