Environmental Engineering Reference
In-Depth Information
Aquatic Life Water Quality Criteria for Tributyltin (TBT) -Final” (USEPA 2003b)
utilizes data from studies of imposex in the dogwhelk, Nucella lapillus , to set the
final chronic criterion.
In calculating aquatic ERLs, the Netherlands includes only data from endpoints
that affect species at the population level, such as survival, growth, and reproduc-
tion (RIVM 2001). However, a broad range of effects is included in the category of
“reproductive effects,” such as histopathological effects on reproductive organs,
spermatogenesis, fertility, pregnancy rate, number of eggs produced, egg fertility,
and hatchability (Slooff 1992). Endpoints used for calculation of criteria, based on
secondary poisoning, include fertility, pregnancy rate, number of live fetuses, pup
mortality, eggshell thinning, egg production, egg fertility, hatchability, and chick
survival (Romijn et al. 1993). Other endpoints, such as immobility or endocrine
disruption, may be used only as evidence in support of derived ERLs, if the end-
points are relevant to the species or are specific to a known toxicant's mode of
action. Carcinogenicity and mutagenicity endpoints are not used because studies
of these endpoints are difficult to evaluate. Also, population level consequences
from carcinogenicity and mutagenicity are unknown (RIVM 2001).
The OECD methodology (1995) prefers use of traditional endpoints, such as
survival, growth, and reproduction; however, biochemical endpoints may be con-
sidered as well, although clear guidance is not given for their use. German policy
makers have recognized the potential for adverse effects posed by endocrine disrup-
tors, but have not yet incorporated these concerns into water quality targets, because
data are unavailable on the presence of endocrine disruptors in water bodies, and
on concentration-dependent effects (BMU 2001). Similarly, the Danish methodology
(Samsoe-Petersen and Pedersen 1995) excludes data for endpoints such as enzyme
activity, or hemoglobin or hormone concentrations because such effects do not
translate easily into population level effects. The Canadian methodology (CCME
1999) accepts test results with pathological, behavioral, and physiological effects
endpoints; however, such studies are regarded as secondary data (used for deriva-
tion of interim guideline values). In South Africa, only lethality (an irreversible
effect) is accepted as an acute endpoint (Roux et al. 1996); any adverse effect is
accepted as an endpoint for chronic data because such data are consistent with the
precautionary approach.
Segner (2005) conducted a review that links exposure and effect for endocrine
disruptors. He presented three cases, in which population-level effects in wildlife
could be linked to environmental substances with endocrine activity: reductions in
dogwhelk ( Nucella lapillus ) populations resulting from imposex caused by exposure
to TBT; reduction in predatory bird populations from eggshell thinning caused by
exposure to DDE (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene);
and decline in Atlantic salmon populations from effects of 4-nonylphenol on the
ability of smolts to osmoregulate. However, only in the case of TBT is there a
strong case for endocrine disruptors actually causing the observed toxic effects.
Matthiessen (2000) points out that, despite this result, it is uncertain that endocrine
effects in individuals produce population effects for other chemicals—the data just
do not exist to draw that conclusion. Triebskorn et al. (2003) undertook a project
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