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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

TCP exhibits chronic effects to fish. The NOEC assigned on the basis of 6 month exposure data.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
4.4 mg/L

Additional information

In the beginning of 2004, a draft report of toxicity tests with two fish species and 1,2,3-trichloropropane was published (NIH 2005). These studies were not included in the CICAD (OECD SIDS 2004) but robust summaries have been prepared. The NIH chose to initiate these studies in guppies (Poecilia reticulata) and medaka (Oryzias latipes) as an exploration of alternate or additional models for examining chemical toxicity and carcinogenicity. The use of small fish species in carcinogenicity testing offered potential advantages as a bioassay test system, including significant savings in cost and time over rodent studies. Groups of 220 guppies (two replicates of 110) and 340 medaka (two replicates of 170) were exposed 1,2,3-trichloropropane in a flow-through system to each of four nominal concentrations 0, 4.5, 9.0 and 18.0 mg/L. Nine months after the test initiation, approximately one-third of the fish from each exposure group were transferred from the exposure system to aquaria receiving 1,2,3-trichloropropane-free water under flow-through conditions. They remained in this system for an additional 4 months (medaka) or 7 months (guppies). Fish remaining in the exposure system continued 1,2,3-trichloropropane exposure for a total of approximately 13 months (medaka) or 16 months (guppies). Concentrations of 1,2,3-trichloropropane in the exposure aquaria were monitored using GC, approximately 3 times each week. Differences between nominal and measured concentrations were less than 3 %. After 9 months the mortality of the guppies was 1.4; 6.4; 7.7 and 14.5 % for 1,2,3-trichloropropane concentrations of 0, 4.5, 9.0 and 18.0 mg/L, respectively. Although the survival of exposed guppies was less than that of the control group at 9 months, guppies in the 18.2 mg/L study group were significantly longer and weighed more than the controls. Observed differences in weight and length between controls and 18.0 mg/L fish was most likely an artefact of the reduced fish numbers in the 18.0 mg/L aquaria (amount of food was not reduced). Under the conditions of this study, 1,2,3-trichloropropane at concentrations of up to 18 mg/L for 16 months was considered carcinogenic for male and female guppies, based on increased incidences of a variety of liver neoplasms. After 9 months the mortality of the medaka was 3.2; 1.8; 4.7 and 8.2 % for 1,2,3-trichloropropane nominal concentrations of 0, 4.5, 9.0 and 18.0 mg/L, respectively. At 9 months, the weights of medaka in the 9.0 and 18.0 mg/L groups were significantly increased. Core-study medaka in the 18.0 mg/L group were both longer and weighed more than the controls at the end of the study. Observed differences in weight and/or length between controls and 9.0 or 18.0 mg/L fish have been an artifact of the reduced fish numbers in these exposure aquaria (amount of food was not reduced). Under the conditions of this study, 1,2,3-trichloropropane at concentrations of up to 18 mg/L for 13 months was considered carcinogenic for male and female medaka, based on increased incidences of a variety of liver neoplasms and papillary adenoma of the gallbladder (OECD SIDS 2004).

NOEC derivation

Intermediary results from these studies allow the derivation of long-term NOECs based on mortality. While in the guppy study a 6 month value is conclusive for the 8.8 mg/L concentration, after 7 month all tested concentrations showed significantly reduced mortality. The medaka experiment delivers a 9 month NOEC of 4.6 mg/L. The survival in the 9.0 and 18.0 mg/L groups indicated that 1,2,3-trichloropropane was chronically toxic to the medaka in this concentrations and reduced survival was evident beginning at 9 months of exposure. Thus the lowest measured concentration of 4.6 mg/L is regarded as NOEC 9 month for the endpoint mortality in the medaka test. However - guppies were more sensitive and even if the comparable derivation of a definitive NOEC is not possible it is clear the NOEC 7 month for guppies is < 4.4 mg/L. Thus in application of the precautionary principle the value 4.4 mg/L is taken as NOEC fish, long-term. One may counter that a lower value should apply because at this level were still effects, but on the other hand the observation is much longer than the standards for this endpoint and thus for the derivation of PNEC according to the standard approaches this assigned NOEC of 4.4 mg/L is acceptable.