Maximum Acceptable Concentration Research Articles

Pesticide residues in four rivers running through an intensive agricultural area, Kilimanjaro, Tanzania

Organochlorine pesticide (OCP) residues were determined in water and bottom-sediments from four rivers running through sugarcane plantations in Kilimanjaro Tanzania. The aim was to assess the levels of pesticide contamination as the rivers are important sources of domestic water in the area. Water samples were extracted by liquid–liquid extraction method, and ultrasonic-assisted liquid-solid extraction coupled with gel permeation chromatography was employed in sediment preparation, before analysis by GC-ECD and GC-MS. Blank and spiked recovery tests were used to validate the analytical procedure. Data were assessed by using descriptive statistics and multivariate analysis to study correlations between different parameters, evaluate the contamination patterns and describe their spatial and seasonal trends. The percentage recoveries ranged from 75.0 ± 2.4 to 89.8 ± 1.5 in water, and 70.5 ± 1.7 to 86.2 ± 2.3 in sediments, which are within the acceptable ranges. The OCP concentrations ranged from trace (endrin) to 120 ng/l (p,p’-DDD) in water, and from trace (aldrin) to 132 ng/g-dry weight (p,p’-DDD) in sediments, and were higher during the dry season. A notable water contamination that exceeded the European Union maximum acceptable concentration for the protection of human health was detected in river Kikavu. @ JASEM Keywords: Pesticide residues, Surface water, Sediment, Environmental contamination

Lead and cadmium accumulation potential and toxicity threshold determined for land cress and spinach

Soil contamination with potentially toxic elements (PTEs) in agricultural lands, in part, is responsible for limiting the crop productivity and the food chain contamination. The objective of this study were to asses the limiting of crop productivity by cadmium (Cd) and lead (Pb), the potential transfer and bioaccumulation of these PTEs in plants, and ultimately the food chain contamination to ensure that the pre-established soil threshold concentrations for Cd and Pb are enough to control food chain exposure to them. Therefore, land cress and spinach were grown in some pots containing a sandy loam soil contaminated with increasing concentrations of Pb and Cd. The concentrations of Pb and Cd in land cress and spinach at any level of soil contamination were compared with the threshold concentrations of Pb and Cd in leafy vegetables as established by the Codex Alimentarius Commission (CAC). A bioaccumulation factor was calculated to estimate the potential transfer of Pb and Cd to the food chain. According to the results, Pb was of more phytotoxicity than Cd. The lower limit of the maximum acceptable concentration of Pb in soil was safe enough to ensure the prevention of the food chain contamination to Pb. Results also showed that growing land cress on contaminated soils was of great potential risk of Pb transfer to the human food chain when compared to spinach. The pre-established maximum acceptable concentration of Cd in soil of 1-20 mg kg -1 was not safe to prevent the contamination of food chain. Cd was of a greater potential of entering the human food chain than Pb.

Application of bioassays in toxicological hazard, risk and impact assessments of dredged sediments

Given the potential environmental consequences of dumped dredged harbour sediments it is vital to establish the potential risks from exposure before disposal at sea. Currently, European legislation for disposal of contaminated sediments at sea is based on chemical analysis of a limited number of well-known contaminants for which maximum acceptable concentrations, action levels (ALs), have been set. The present paper addresses the issue of the applicability of in vitro and in vivo bioassays for hazard, risk and local impact assessment of dredged polluted sediments to be disposed of at sea. It discusses how and to what extent selected bioassays can fill in the gaps left open by chemical analysis and the way in which the bioassays may contribute to the present licensing system for disposal. Three different purposes for application were distinguished: the most basic application (A) is a rapid determination of the hazard (potential toxicity) of dredged sediments which is then compared to ALs in a licensing system. As with chemical analysis on whole sediment extracts, the bioavailability of the chemicals is not taken into account. As in vitro assays with sediment extracts are not sensitive to matrix effects, a selection of specific in vitro bioassays can be suitable fast and standardized additions for the licensing system. When the outcome of (A) does not convincingly demonstrate whether the sediment is clean enough or too polluted, further bioanalysis can help the decision making process (B). More aspects of the mostly unknown complex chemical mixtures are taken into account, including the bioavailability and chronic toxicity focusing on ecologically relevant endpoints. The ecotoxicological pressure imposed by the dredged sediments can be quantified as the potentially affected fraction (PAF) based on chemical or biological analysis of levels of contaminants in sediment or biota. To validate the predicted risk, the actual impact of dumped harbour sediments on local ecosystems (C) can be determined using a dedicated set of in vitro and in vivo bioassays as well as bio-indicators selected based on the information obtained from (A) and (B) and on the characteristics of the local ecosystem. Conversely, the local sediment impact assessment (C) can direct fine-tuning of the selection of chemical and bioassay analyses and for setting safe levels in the licensing system. It is concluded that in vitro and in vivo bioassays and biological indicators are useful tools in the process of hazard, ecotoxicological risk and impact assessment of dredged harbour sediments, provided they are consciously chosen and quality criteria for assay performance are defined.

Doses to children from intakes by ingestion

In this article, sensitivities and doses to children from intakes of radionuclides by ingestion were studied relative to adults. Generally speaking, doses to children were higher due to their higher radiosensitiveness to many radionuclides, even though they consume less food and water than adults. Therefore, the action levels in the Canadian guidelines for the restriction of radioactively contaminated food and water following a nuclear emergency were selected as the most restrictive among the six age groups that could lead to an individual receiving a dose equal to a specified intervention level of 1 mSv. For non-emergency situations, the specified intervention level is 0.1 mSv. At such a low intervention level, the maximum acceptable concentrations (MAC) in drinking water are normally derived for adults. Although this is a common practice for guidelines in non-emergency operations, for those radionuclides when the doses to children are more than 10 times higher than the doses to adults, the MAC in non-emergency situations should be limited to, at least, as restrictive as the action levels for interventional action following a nuclear emergency.

A fast method to assess the composition of a polyolefin: An application to compliance testing of food contact materials

AbstractFor plastics materials intended to be in contact with food, recent EU regulations, 72/2002/EC and 1935/2004/EC, enforce the assessment of the migration of 502 substances of the 932 positively listed substances. As mathematical modeling has been proposed to overcome such considerable effort in particular by providing maximum acceptable concentrations in the formulation, the compliance testing problem is efficiently reduced to the identification of substances and to their extent in initial materials. This work examines a fast identification and quantification procedure based on a semisupervised deconvolution procedure of FTIR spectra of polymer extracts in dichloromethane. The inversion procedure was implemented as a Tikhonov least‐square problem and designed to work on large and open dictionary of substances by combining both spectra of reference additives and normalized responses of typical chemical functions. The sparsity of the overall solution was fulfilled with non‐negativity constraints, while traces were detected by an iterative reweighting and stochastic resonance. The whole methodology was calibrated onto 21 typical additives of polyolefins and satisfactory tested on numerical examples and on extracts of processed films in high‐density polyethylene including up to eight unknown compounds. Maps of possible confusions and biases were generated for all tested substances. The mass balance laws for molecules belonging to similar classes of additives were particularly highlighted. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of lead on zooplankton dynamics in Challawa River, Kano State, Nigeria

Lead concentration was determined with the aid of Atomic Absorption Spectrophotometer while zooplankton were collected with the aid of plankton net and analysed microscopically to assess their diversity and density in the Challawa River at four selected sites on fortnight basis between July 2006 and December 2007. The mean lead concentration was between 125 mg/L and 2.84 mg/L, far above maximum acceptable and allowable concentrations in drinking water of 0.05 mg/L and 0.10 mg/L respectively (WHO, 1996). The mean zooplankton density ranged between 3.09 Org/L and 10.26 Org/L. Only five protozoan, two insect, four copepod (plus one naplius I), one cladoceran and five rotifer species were identified during the study. The river quality decreased down stream, with least plankton recovery of 4 species at the industrial effluent inflow site and highest off-stream (site A) with 14 species. The site that experiences a direct inflow of industrial effluent was the most polluted (Odum’s Index = 0.22). Significant differences occurred in the lead concentration between the sites (P

Determination of Activity Concentration Levels of 238U, 232Th, and 40K in Drinking Water in a Gold Mine in Ghana

The study of the activity concentration levels of uranium, thorium and potassium in drinking water from different locations in a gold mine in the Ashanti Region of Ghana was conducted using gamma spectrometry. The mean outdoor absorbed gamma dose rates at 1 m from the water were 0.524 nGy h, 0.422 nGy h, and 0.252 nGy h for groundwater, surface water, and treated water, respectively. The results obtained for the activity concentration levels of U and Th are found to be within the maximum acceptable concentration levels of 3.0 Bq L and 0.6 Bq L, respectively, recommended by the World Health Organization. The overall mean outdoor gamma dose rate is 0.41 nGy h and the corresponding outdoor annual effective dose obtained for adult members of the public for drinking water from the mines is 3.58 muSv y. This value is found to be within the 10.0 muSv per annum (0.01 mSv per annum) for public exposure control set by the World Health Organization. Therefore, the mining activities on drinking water studied did not show any significant radiological health implications on the public.

Assessment of nitrate contamination of Lidder catchment Kashmir, India

Nitrate contamination in the groundwater from various sources is one of the major problems of water resources in Liddercatchment, Kashmir. Systematic sampling was carried out during summer 2007, with a view to understand the source of nitrate ions in the groundwater of the Lidder catchment. Twelve sample sites were selected and samples were taken for a baseline study to understand the geochemistry of the groundwater and to assess the overall physico-chemical characteristics. Results showed that NO3− concentration in ranged from 18.72 mg/L to 75.93 mg/L with an average of 47.03 mg/L. More than 80% (83.33%) of the samples collected from various sampling stations had nitrate concentrations exceeding the threshold value of 20 mg/L, and 58.33% of the samples collected had nitrate concentrations higher than 50 mg/L, the maximum acceptable nitrate concentration for drinking water. There is a wide spatial variation in the nitrate concentration in the groundwater. Monitoring the water quality of various sampling stations showed that the lowest concentrations of nitrate were found in the wet season (January, February, and December), while the highest concentrations were found in the dry season (August, September). Numerous human perturbations have been detected affecting the water quality of Lidder catchment. Disposal of sewage and animal wastes was found to contribute about 85% of total nitrate pollution in the study area. Based on the trend analysis (using previous data), future scenario of nitrate pollution has been predicted in the study area. The results of this study are useful to highlight one of the most important environmental problems, namely the degradation of the water quality, and may serve to alert and encourage local and national authorities to take substantial steps and actions to protect and manage water quality.

Cadmium concentration in muscle, liver and kidney of sheep slaughtered in Falavarjan abattoir, Iran

The aim of the present study was to investigate the levels of cadmium in sheep's muscle, liver and kidney from Isfahan and also to compare them with the levels reported in several other countries and with the maximum tolerance levels for the human consumption. The samples of muscle, liver and kidney of 60 animals around 1 to 6 years old were collected from the carcasses slaughtered in Flavarjan abattoir, Isfahan. Samples (acid digested and cadmium concentrations) were determined by graphite furnace atomic absorption spectrophotometry (GFAAS). The mean fresh weight concentrations in muscle, liver and kidney were about 0.0017 mg/kg, 0.0743 mg/kg and 0.02290 mg/kg, respectively. The mean concentration of cadmium in tissue samples was generally lower than the maximum acceptable concentration in European Commission (EC). Statistical analysis revealed a significant difference in cadmium concentration of liver and kidney between various age groups (p < 0.05).

Monitoring of organochlorine pesticides in the surface waters from Mid-Black Sea Region, Turkey

The levels of 16 organochlorine pesticides (OCPs) in surface water in Mid-Black Sea Region in Turkey were investigated to evaluate their potential pollution and risks. The analysis of OCPs extracted by C-18 solid phase extract was performed using Fisions Mega II Series gas chromatograph coupled by electron capture detector. Surface water samples have been collected seasonally from ten rivers for a period of 1 year. The most commonly encountered OCPs in surface water were the isomers of hexachlorocyclohexane, dieldrin, p,p-DDD, and heptachlor epoxide. In some cases the concentrations detected were higher than the qualitative target levels set by the European Union, especially for δ-hexachlorocyclohexane. The concentration levels found are lower than the EU maximum acceptable concentration of 0.10 μg/l for all compounds examined, except for δ-HCH in two samples (0.2505 μg l(-1) in the S-5 and 0.2046 μg l(-1) in the S-10). The occurrence of these compounds in Mid-Black Sea Region surface waters can be attributed to intense agricultural activity as well as to transboundary pollution.

Effects of Cooking and Subcellular Distribution on the Bioaccessibility of Trace Elements in Two Marine Fish Species

In current human health risk assessment, the maximum acceptable concentrations of contaminants in food are mostly based on the total concentrations. However, the total concentration of contaminants may not always reflect the available amount. Bioaccessibility determination is thus required to improve the risk assessment of contaminants. This study used an in vitro digestion model to assess the bioaccessibility of several trace elements (As, Cd, Cu, Fe, Se, and Zn) in the muscles of two farmed marine fish species (seabass Lateolabrax japonicus and red seabream Pagrosomus major ) of different body sizes. The total concentrations and subcellular distributions of these trace elements in fish muscles were also determined. Bioaccessibility of these trace elements was generally high (>45%), and the lowest bioaccessibility was observed for Fe. Cooking processes, including boiling, steaming, frying, and grilling, generally decreased the bioaccessibility of these trace elements, especially for Cu and Zn. The influences of frying and grilling were greater than those of boiling and steaming. The relationship of bioaccessibility and total concentration varied with the elements. A positive correlation was found for As and Cu and a negative correlation for Fe, whereas no correlation was found for Cd, Se, and Zn. A significant positive relationship was demonstrated between the bioaccessibility and the elemental partitioning in the heat stable protein fraction and in the trophically available fraction, and a negative correlation was observed between the bioaccessibility and the elemental partitioning in metal-rich granule fraction. Subcellular distribution may thus affect the bioaccessibility of metals and should be considered in the risk assessment for seafood safety.

Heavy metal and trace element accumulation in muscle, liver and gills of the Pontic shad (Alosa immaculata Bennet 1835) from the Danube River (Serbia)

Pontic shad ( Alosa immaculata Bennet 1835) is an anadromous species that lives in the heavily polluted north-western part of the Black Sea and migrates into the Danube River to spawn. To assess their heavy metal contamination levels, samples of Pontic shad were collected at 863 river kilometre of the Danube River. Muscle, liver and gill samples were prepared using microwave digestion, and the analysis of Al, As, Cd, Cu, B, Ba, Fe, Mg, Sr, Zn, Li, Co, Cr, Mn, Mo, Ni and Pb was performed with inductively-coupled plasma-optic emission spectroscopy (ICP-OES). Significant differences in concentrations of analyzed elements were observed among different tissues, as well as between the genders. Al, Sr, Ba, Mg, and Li had the highest concentrations in gills, while Cd, Cu, Zn, Fe and B were highest in the liver. While the muscle had the lowest concentrations of most of the analyzed elements, it had the highest concentration of As. This study has revealed that the concentrations of Cd and As in Pontic shad muscle tissue were above the maximum acceptable concentrations for human consumption, thus precautions need to be taken in order to prevent future heavy metal contamination.

Nitrate contamination: A major challenge to water and human health

Nitrate contamination of the world’s groundwater supply poses a serious human health threat. High nitrate levels found in drinking water have been proven to be the cause for numerous health conditions across the world. In many countries, public concern over the deterioration of groundwater quality from nitrate contamination has grown significantly in recent years. This concern has focused increasingly on anthropogenic sources as the potential cause of the problem. Systematic sampling was carried out in the year 2008 with a view to understand the source of nitrate contamination in Lidder catchment, Kashmir (India). Twelve sample sites were selected and samples were taken for a baseline study to understand the geochemistry of the groundwater. Results showed that fifty percent of the samples collected had nitrate concentrations higher than 50 mg·L -1 , the maximum acceptable nitrate concentration for drinking water. There is a wide spatial variation in the nitrate concentration in groundwater. Monitoring the water quality of various sampling stations showed that the lowest concentrations of nitrate were found in the wet season, while the highest concentrations were found in the dry season. Numerous human perturbations have been detected affecting the water quality of Lidder catchment. The results of this study are useful to highlight one of the most important environmental problems, namely the degradation of the water quality, and may serve to alert and encourage local and national authorities to take substantial steps and actions to protect and manage water quality; otherwise the Lidder water may turn into poison.

Improved method for the complete separation of gross alpha and beta in drinking water

During this work, a modified methodology for the separation of gross alpha and beta activity from potable water was established. Complete separation of gross alpha activity was carried out by Fe(OH)3 and BaSO4 precipitation whereas gross beta activity was scavenged by Ca-oxalate and AMP (ammonium molybdate phosphates). The validation of the results was carried out by laboratory spiked experiments, which show a recovery of gross radioactivity in the range of 90–98% with the new methodology. The detection limits using this methodology are 20 mBq/l and 2 mBq/l for gross beta and alpha respectively. These detection limits are two orders of magnitude lower than the maximum acceptable concentration as prescribed by World Health Organisation (WHO) of gross alpha and gross beta activity i.e. less than 0.1 Bq/L and 1 Bq/L, respectively.

Atrazine: its occurrence and treatment in water

A comprehensive review of atrazine including its use, properties, environmental fate, toxicological effects, occurrence in water, a summary of criteria for drinking water and the efficiency of various water treatment options for its removal was conducted. Atrazine is ubiquitous in surface water, groundwater, and precipitation, due to its widespread use for the control of broadleaf and grassy weeds mainly in corn crops. Atrazine is considered a priority substance by the USEPA, Agriculture Canada, and the European Commission. It causes developmental deformities and impacts behavior in frogs and fish. Atrazine has been implicated as a possible endocrine disrupting compound and has been associated with various cancers in humans such as stomach, prostate, breast, and non-Hodgkin's lymphoma. Guidelines and standards governing maximum acceptable concentrations in fresh and marine waters are scarce and those for drinking water vary significantly between agencies. The effectiveness of tertiary water treatment technologies for the removal of atrazine demonstrates varying efficiencies. Variations in the quality of source water and the presence of natural organic matter present significant challenges for its removal.

Acute and chronic toxicity of ammonia, nitrite, and nitrate to the endangered topeka shiner (Notropis topeka) and fathead minnows (Pimephales promelas)

Toxicity tests with ammonia, nitrite, and nitrate were conducted on the endangered Topeka shiner (Notropis topeka) to determine if current U.S. Environmental Protection Agency (U.S. EPA) water quality criteria are protective of this species. Results from acute lethal and chronic growth tests are reported for both Topeka shiners and fathead minnows (Pimephales promelas). Embryo-larval tests were conducted with only fathead minnows because Topeka shiner embryos were not available. Predicted outcomes for Topeka shiner embryo-larval toxicity endpoints were calculated by comparing relationships between growth tests and embryo-larval tests for fathead minnows and extrapolating those relationships to Topeka shiners. Results show that the U.S. EPA's criterion for total ammonia-nitrogen (TAN), 1.24 mg/L when early life stages are present, would be protective, given that our most sensitive result was a predicted maximum acceptable toxicant concentration (MATC) for Topeka shiners at 5.63 mg/L TAN, calculated from the fathead minnow chronic embryo-larval test. The U.S. EPA's criterion for nitrite (5 mg/L) would not be protective, given that our most sensitive result was a predicted MATC for Topeka shiners of 3.97 mg/L NO2-N, calculated from the fathead minnow chronic embryo-larval test. However, nitrite is generally transient, and unpublished field data show levels far lower than the criterion. Finally, the U.S. EPA's recommendation of a maximum of 90 mg/L NO3-N for the protection of warmwater fishes would protect Topeka shiners but not fathead minnows. For Topeka shiners, the MATC from the 30-d juvenile growth test was 360 mg/L NO3-N, but for fathead minnows, the MATC was 84 mg/L. More field sampling may be needed to determine if levels comply with criteria, especially in Topeka shiner critical habitat.

An Ecological Risk Assessment of the Acute and Chronic Effects of the Herbicide Clopyralid to Rainbow Trout (Oncorhynchus mykiss)

Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) is a pyridine herbicide frequently used to control invasive, noxious weeds in the northwestern United States. Clopyralid exhibits low acute toxicity to fish, including the rainbow trout (Oncorhynchus mykiss) and the threatened bull trout (Salvelinus confluentus). However, there are no published chronic toxicity data for clopyralid and fish that can be used in ecological risk assessments. We conducted 30-day chronic toxicity studies with juvenile rainbow trout exposed to the acid form of clopyralid. The 30-day maximum acceptable toxicant concentration (MATC) for growth, calculated as the geometric mean of the no observable effect concentration (68 mg/L) and the lowest observable effect concentration (136 mg/L), was 96 mg/L. No mortality was measured at the highest chronic concentration tested (273 mg/L). The acute:chronic ratio, calculated by dividing the previously published 96-h acutely lethal concentration (96-h ALC(50); 700 mg/L) by the MATC was 7.3. Toxicity values were compared to a four-tiered exposure assessment profile assuming an application rate of 1.12 kg/ha. The Tier 1 exposure estimation, based on direct overspray of a 2-m deep pond, was 0.055 mg/L. The Tier 2 maximum exposure estimate, based on the Generic Exposure Estimate Concentration model (GEENEC), was 0.057 mg/L. The Tier 3 maximum exposure estimate, based on previously published results of the Groundwater Loading Effects of Agricultural Management Systems model (GLEAMS), was 0.073 mg/L. The Tier 4 exposure estimate, based on published edge-of-field monitoring data, was estimated at 0.008 mg/L. Comparison of toxicity data to estimated environmental concentrations of clopyralid indicates that the safety factor for rainbow trout exposed to clopyralid at labeled use rates exceeds 1000. Therefore, the herbicide presents little to no risk to rainbow trout or other salmonids such as the threatened bull trout.

Melamine contamination

In the summer of 2008, serious illnesses and deaths of babies in China were linked to melamine-tainted powdered infant formula. Melamine contains several metabolites, such as ammeline, ammelide, and cyanuric acid, and has been used for the adulteration of foods or milk to increase their apparent protein content. It is assumed that melamine and its metabolites are absorbed in the gastrointestinal tract, and precipitate in the kidney to form crystals. A new tolerable daily intake of 0.2 mg kg(-1) body weight was adapted by the World Health Organization in 2008. This paper reviews the variety of analytical methods that have been used for the analysis of melamine in food. The limit of detection of these various methods is 0.05-100 ppm. The maximum acceptable concentration in food has been set at 50 ppb by the US FDA. A fast and ultrasensitive procedure for screening, detection, and characterization of melamine and its derivative compounds needs to be established. Currently, mass-spectrometry technologies provide an alternative to derivatization for regulatory analysis of food.

Speciation of Cr(VI) in environmental samples in the vicinity of the ferrochrome smelter

The impact of ferrochrome smelter on the contamination of its environment with toxic hexavalent chromium, Cr(VI), was assessed by analyzing smelter dusts, soil, grass and tree barks. For the separation of Cr(VI) from Cr(III), solid samples were treated with 0.1 M Na 2CO 3 and filtered through hydrophilic PDVF 0.45 μm filter prior to the determination of Cr(VI) by electrothermal atomic absorption spectrometry (ET–AAS). Ferrochrome smelter dust was found to contain significant levels of Cr(VI), viz. 43.5 μg g −1 (cyclone dust), 2710 μg g −1 (fine dust), and 7800 μg g −1 (slimes dust) which exceeded the maximum acceptable risk concentration (20 μg g −1). The concentration of Cr(VI) in environmental samples of grass (3.4 ± 0.2), soil (7.7 ± 0.2), and tree bark (11.8 ± 1.2) collected in the vicinity of the chrome smelter were higher as compared with the same kind of samples collected from uncontaminated area. The results of the investigation show that ferrochrome smelter is a source of environmental pollution with contamination factors of Cr(VI) ranging between 10 and 50.

Partial or total replacement of fish meal by local agricultural by-products in diets of juvenile African catfish (Clarias gariepinus): growth performance, feed efficiency and digestibility

The study was undertaken to evaluate the growth performance and feed utilization of African catfish, Clarias gariepinus, fed six diets (D) in which fishmeal (FM) was gradually replaced by a mixture of local plant by-products. In diets 1 and 2, FM (250 g kg-1) was replaced by sunflower oil cake (SFOC). In diets 3 and 4, FM (250 and 150 g kg-1, respectively) was replaced by SFOC and bean meal (BM) while FM was totally substituted by a mixture of groundnut oil cake (GOC), BM and SFOC in diets 5 and 6. Sunflower oil cake was cooked, soaked or dehulled in order to determine the appropriate processing techniques for improving the SFOC nutritive value and to evaluate the apparent digestibility coefficient (ADC) values of the alternative diets. No significant differences were observed for daily feed intake, weight gain, specific growth rate (SGR) and feed efficiency (FE) among fish fed D1, D2, D3 (250 g kg-1 FM), D4 (150 g kg-1 FM) and D6 (0 g kg-1 FM). The highest SGR (3.2% per day) and FE (1.2) were achieved in fish fed D3, and the lowest in fish fed D5 (0% FM), suggesting a maximum acceptable dietary concentration of hulled SFOC below 250 g kg-1 in African catfish juveniles. Protein efficiency ratio ranged from 2.2 to 3.2 for all dietary treatments and was positively influenced by FM inclusion. African catfish were able to digest plant protein very efficiently in all diets tested. ADC of protein ranged from 88.6 to 89.5%, while ADC of energy was relatively low for diets containing hulled sunflower oilcake (71-74%) and high when sunflower oilcake was dehulled (78.6-81.3%). Similarly, ADC of dry matter was higher when sunflower was dehulled (72.1%) when compared with crude SFOC (60.5%). Soaking increased ADC values for neutral detergent fibre (NDF), dry matter, energy, protein and amino acids (AA). There were no significant differences in protein ADCs (88-90%) with increased levels of dietary vegetable ingredients. Both soaking and dehulling of sunflower before incorporation helped in the reduction of NDF, antitrypsin and tannins. Digestibility of all AA was generally high, greater than 90% for both indispensable and non-indispensable AA. Based on the data obtained, it was possible to totally replace menhaden fish meal with a mixture of vegetable proteins (72% of total dietary protein) when diets contained a relatively low percentage of animal protein (28% based on blood meal and chicken viscera meal) without negative effects.