19 research outputs found
Hubungan Penggunaan Dan Penanganan Pestisida Pada Petani Bawang Merah Terhadap Residu Pestisida Dalam Tanah Di Lahan Pertanian Desa Wanasari Kecamatan Wanasari Kabupaten Brebes
Excessive use of pesticides causing pollution and environmental damage agriculture. Examination in Brebes on 31 samples of fruits and vegetables, found 22% of samples contain detectable residues of organophosphate and found two soil samples (10%) contained residues organochlorin. The purpose of this study was to determine the relationship of the use and handling of pesticides on their onion farmers against pesticide residues in the soil on agricultural land Wanasari Village, District Wanasari, Brebes. This study is observational method with cross sectional approach. The population in this study were all farmers in the Wanasari conducting spraying. Collecting data using the tool Banu questionnaire and examination of pesticide residues in soil using GC-MS Gas Chromatography - Mass Spectrometry. The results of this study are of 55 69.1 onion farmers use pesticides are not good. The use of pesticides covering 80% is not good in mixing pesticides, 87.3% use a smaller dose, 49.1% use pesticides that are not registered with the Ministry of Agriculture, 87.3% is not good in the way of spraying and 87.3 does well in frequency spraying. Handling pesticides in agricultural land is not good 59.1%, ie 74.5% is not good in handling pesticide containers, 90.9% is not good in storage of pesticides, 89.1% is not good in handling a spill and 87.3% did not either in place to clean pesticide containers. The research result is negative soil samples pesticide residues. The conclusion was that no pesticide residue class organochlorin
Development and Evaluation of a Database of Dietary Bioaccumulation Test Data for Organic Chemicals in Fish
Dietary
bioaccumulation tests for fish have been conducted for
about 40 years. Standardized test guidance has recently been developed.
Test metrics of primary scientific and regulatory interest are the
whole body depuration rate constant (<i>k</i><sub>T</sub>), whole body growth corrected depuration rate constant (<i>k</i><sub>Tg</sub>), and corresponding chemical half-lives (<i>t</i><sub>1/2</sub> and <i>t</i><sub>1/2g</sub>),
dietary chemical absorption efficiency (AE), and biomagnification
factor (BMF). A database of 3032 measurement end points for 477 discrete
organic chemicals including 964 half-lives, 1199 AEs and 869 BMFs
from 19 species (primarily trout and carp) was developed from the
literature. Biological properties (e.g., organism weight, lipid content)
and exposure conditions (e.g., temperature, feeding rate, dietary
lipid content, exposure duration) are documented. Test chemicals range
in molar mass from 120 to 1423 g·mol<sup>–1</sup> with
log octanol–water partition coefficients (<i>K</i><sub>OW</sub>) ranging from 0.8 to 14.3; 50% of the database entries
are for polychlorinated biphenyls. The measured end points are derived
from various protocols and sources of variability are described. The
data are evaluated and categorized using proposed data quality (confidence)
criteria derived from the standardized test protocol providing initial
guidance for data users. Half-lives range from 0.13 to 2600 days;
however, approximately 54% have an identifiable source of uncertainty.
The data suggest that chemicals absorbed from the gastrointestinal
tract with a log <i>K</i><sub>OW</sub> ≥ ∼5
and at least as high as ∼9 have biomagnification potential
in fish. A mechanistic bioaccumulation model is compared to the measured
data and used to illustrate the influence of growth and biotransformation
rates on the BMF
Development and Evaluation of a Database of Dietary Bioaccumulation Test Data for Organic Chemicals in Fish
Dietary
bioaccumulation tests for fish have been conducted for
about 40 years. Standardized test guidance has recently been developed.
Test metrics of primary scientific and regulatory interest are the
whole body depuration rate constant (<i>k</i><sub>T</sub>), whole body growth corrected depuration rate constant (<i>k</i><sub>Tg</sub>), and corresponding chemical half-lives (<i>t</i><sub>1/2</sub> and <i>t</i><sub>1/2g</sub>),
dietary chemical absorption efficiency (AE), and biomagnification
factor (BMF). A database of 3032 measurement end points for 477 discrete
organic chemicals including 964 half-lives, 1199 AEs and 869 BMFs
from 19 species (primarily trout and carp) was developed from the
literature. Biological properties (e.g., organism weight, lipid content)
and exposure conditions (e.g., temperature, feeding rate, dietary
lipid content, exposure duration) are documented. Test chemicals range
in molar mass from 120 to 1423 g·mol<sup>–1</sup> with
log octanol–water partition coefficients (<i>K</i><sub>OW</sub>) ranging from 0.8 to 14.3; 50% of the database entries
are for polychlorinated biphenyls. The measured end points are derived
from various protocols and sources of variability are described. The
data are evaluated and categorized using proposed data quality (confidence)
criteria derived from the standardized test protocol providing initial
guidance for data users. Half-lives range from 0.13 to 2600 days;
however, approximately 54% have an identifiable source of uncertainty.
The data suggest that chemicals absorbed from the gastrointestinal
tract with a log <i>K</i><sub>OW</sub> ≥ ∼5
and at least as high as ∼9 have biomagnification potential
in fish. A mechanistic bioaccumulation model is compared to the measured
data and used to illustrate the influence of growth and biotransformation
rates on the BMF
Model for Screening-Level Assessment of Near-Field Human Exposure to Neutral Organic Chemicals Released Indoors
Screening organic
chemicals for hazard and risk to human health
requires near-field human exposure models that can be readily parametrized
with available data. The integration of a model of human exposure,
uptake, and bioaccumulation into an indoor mass balance model provides
a quantitative framework linking emissions in indoor environments
with human intake rates (<i>iR</i>s), intake fractions (<i>iF</i>s) and steady-state concentrations in humans (<i>C</i>) through consideration of dermal permeation, inhalation,
and nondietary ingestion exposure pathways. Parameterized based on
representative indoor and adult human characteristics, the model is
applied here to 40 chemicals of relevance in the context of human
exposure assessment. Intake fractions and human concentrations (<i>C</i><sub>U</sub>) calculated with the model based on a unit
emission rate to air for these 40 chemicals span 2 and 5 orders of
magnitude, respectively. Differences in priority ranking based on
either <i>iF</i> or <i>C</i><sub>U</sub> can be
attributed to the absorption, biotransformation and elimination processes
within the human body. The model is further applied to a large data
set of hypothetical chemicals representative of many in-use chemicals
to show how the dominant exposure pathways, <i>iF</i> and <i>C</i><sub>U</sub> change as a function of chemical properties
and to illustrate the capacity of the model for high-throughput screening.
These simulations provide hypotheses for the combination of chemical
properties that may result in high exposure and internal dose. The
model is further exploited to highlight the role human contaminant
uptake plays in the overall fate of certain chemicals indoors and
consequently human exposure
Revisiting the Contributions of Far- and Near-Field Routes to Aggregate Human Exposure to Polychlorinated Biphenyls (PCBs)
The
general population is exposed to polychlorinated biphenyls
(PCBs) by consuming food from far-field contaminated agricultural
and aquatic environments, and inhalation and nondietary ingestion
in near-field indoor or residential environments. Here, we seek to
evaluate the relative importance of far- and near-field routes by
simulating the time-variant aggregate exposure of Swedish females
to PCB congeners from 1930 to 2030. We rely on a mechanistic model,
which integrates a food-chain bioaccumulation module and a human toxicokinetic
module with dynamic substance flow analysis and nested indoor-urban-rural
environmental fate modeling. Confidence in the model is established
by successfully reproducing the observed PCB concentrations in Swedish
human milk between 1972 and 2016. In general, far-field routes contribute
most to total PCB uptake. However, near-field exposure is notable
for (i) children and teenagers, who have frequent hand-to-mouth contact,
(ii) cohorts born in earlier years, e.g., in 1956, when indoor environments
were severely contaminated, and (iii) lighter chlorinated congeners.
The relative importance of far- and near-field exposure in a cross-section
of individuals of different age sampled at the same time is shown
to depend on the time of sampling. The transition from the dominance
of near- to far-field exposure that has happened for PCBs may also
occur for other chemicals used indoors
Estimating Screening-Level Organic Chemical Half-Lives in Humans
Relatively
few measured data are available for the thousands of
chemicals requiring hazard and risk assessment. The whole body, total
elimination half-life (<i>HL</i><sub>T</sub>) and the whole
body, primary biotransformation half-life (<i>HL</i><sub>B</sub>) are key parameters determining the extent of bioaccumulation,
biological concentration, and risk from chemical exposure. A one-compartment
pharmacokinetic (1-CoPK) mass balance model was developed to estimate
organic chemical <i>HL</i><sub>B</sub> from measured <i>HL</i><sub>T</sub> data in
mammals. Approximately 1900 <i>HL</i>s for human adults
were collected and reviewed and the 1-CoPK model was parametrized
for an adult human to calculate <i>HL</i><sub>B</sub> from <i>HL</i><sub>T</sub>. Measured renal clearance and whole body
total clearance data for 306 chemicals were used to calculate empirical <i>HL</i><sub>B,emp</sub>. The <i>HL</i><sub>B,emp</sub> values and other measured data were used to corroborate the 1-CoPK <i>HL</i><sub>B</sub> model calculations. <i>HL</i>s
span approximately 7.5 orders of magnitude from 0.05 h for nitroglycerin
to 2 × 10<sup>6</sup> h for 2,3,4,5,2′,3′,5′,6′-octachlorobiphenyl
with a median of 7.6 h. The automated Iterative Fragment Selection
(IFS) method was applied to develop and evaluate various quantitative
structure–activity relationships (QSARs) to predict <i>HL</i><sub>T</sub> and <i>HL</i><sub>B</sub> from
chemical structure and two novel QSARs are detailed. The <i>HL</i><sub>T</sub> and <i>HL</i><sub>B</sub> QSARs show similar
statistical performance; that is, <i>r</i><sup>2</sup> =
0.89, <i>r</i><sup>2‑ext</sup> = 0.72 and 0.73 for
training and external validation sets, respectively, and root-mean-square
errors for the validation data sets are 0.70 and 0.75, respectively
Application of Mass Balance Models and the Chemical Activity Concept To Facilitate the Use of in Vitro Toxicity Data for Risk Assessment
Practical,
financial, and ethical considerations related to conducting
extensive animal testing have resulted in various initiatives to promote
and expand the use of in vitro testing data for chemical evaluations.
Nominal concentrations in the aqueous phase corresponding to an effect
(or biological activity) are commonly reported and used to characterize
toxicity (or biological response). However, the true concentration
in the aqueous phase can be substantially different from the nominal.
To support in vitro test design and aid the interpretation of in vitro
toxicity data, we developed a mass balance model that can be parametrized
and applied to represent typical in vitro test systems. The model
calculates the mass distribution, freely dissolved concentrations,
and cell/tissue concentrations corresponding to the initial nominal
concentration and experimental conditions specified by the user. Chemical
activity, a metric which can be used to assess the potential for baseline
toxicity to occur, is also calculated. The model is first applied
to a set of hypothetical chemicals to illustrate the degree to which
test conditions (e.g., presence or absence of serum) influence the
distribution of the chemical in the test system. The model is then
applied to set of 1194 real substances (predominantly from the ToxCast
chemical database) to calculate the potential range of concentrations
and chemical activities under assumed test conditions. The model demonstrates
how both concentrations and chemical activities can vary by orders
of magnitude for the same nominal concentration
DataSheet1_In vitro biotransformation assays using fish liver cells: Comparing rainbow trout and carp hepatocytes.pdf
Biotransformation assays using primary hepatocytes from rainbow trout, Oncorhynchus mykiss, were validated as a reliable in vitro tool to predict in vivo bioconcentration factors (BCF) of chemicals in fish. Given the pronounced interspecies differences of chemical biotransformation, the present study aimed to compare biotransformation rate values and BCF predictions obtained with hepatocytes from the cold-water species, rainbow trout, to data obtained with hepatocytes of the warm-water species, common carp (Cyprinus carpio). In a first step, we adapted the protocol for the trout hepatocyte assay, including the cryopreservation method, to carp hepatocytes. The successful adaptation serves as proof of principle that the in vitro hepatocyte biotransformation assays can be technically transferred across fish species. In a second step, we compared the in vitro intrinsic clearance rates (CLin vitro, int) of two model xenobiotics, benzo[a]pyrene (BaP) and methoxychlor (MXC), in trout and carp hepatocytes. The in vitro data were used to predict in vivo biotransformation rate constants (kB) and BCFs, which were then compared to measured in vivo kB and BCF values. The CLin vitro, int values of BaP and MXC did not differ significantly between trout and carp hepatocytes, but the predicted BCF values were significantly higher in trout than in carp. In contrast, the measured in vivo BCF values did not differ significantly between the two species. A possible explanation of this discrepancy is that the existing in vitro-in vivo prediction models are parameterized only for trout but not for carp. Therefore, future research needs to develop species-specific extrapolation models.</p
Chemical Space Covered by Applicability Domains of Quantitative Structure–Property Relationships and Semiempirical Relationships in Chemical Assessments
A significant number of chemicals registered in national
and regional
chemical inventories require assessments of their potential “hazard”
concerns posed to humans and ecological receptors. This warrants knowledge
of their partitioning and reactivity properties, which are often predicted
by quantitative structure–property relationships (QSPRs) and
other semiempirical relationships. It is imperative to evaluate the
applicability domain (AD) of these tools to ensure their suitability
for assessment purpose. Here, we investigate the extent to which the
ADs of commonly used QSPRs and semiempirical relationships cover seven
partitioning and reactivity properties of a chemical “space”
comprising 81,000+ organic chemicals registered in regulatory and
academic chemical inventories. Our findings show that around or more
than half of the chemicals studied are covered by at least one of
the commonly used QSPRs. The investigated QSPRs demonstrate adequate
AD coverage for organochlorides and organobromines but limited AD
coverage for chemicals containing fluorine and phosphorus. These QSPRs
exhibit limited AD coverage for atmospheric reactivity, biodegradation,
and octanol–air partitioning, particularly for ionizable organic
chemicals compared to nonionizable ones, challenging assessments of
environmental persistence, bioaccumulation capability, and long-range
transport potential. We also find that a predictive tool’s
AD coverage of chemicals depends on how the AD is defined, for example,
by the distance of a predicted chemical from the centroid of the training
chemicals or by the presence or absence of structural features
Risk-Based High-Throughput Chemical Screening and Prioritization using Exposure Models and in Vitro Bioactivity Assays
We present a risk-based
high-throughput screening (HTS) method
to identify chemicals for potential health concerns or for which additional
information is needed. The method is applied to 180 organic chemicals
as a case study. We first obtain information on how the chemical is
used and identify relevant use scenarios (e.g., dermal application,
indoor emissions). For each chemical and use scenario, exposure models
are then used to calculate a chemical intake fraction, or a product
intake fraction, accounting for chemical properties and the exposed
population. We then combine these intake fractions with use scenario-specific
estimates of chemical quantity to calculate daily intake rates (iR;
mg/kg/day). These intake rates are compared to oral equivalent doses
(OED; mg/kg/day), calculated from a suite of ToxCast in vitro bioactivity
assays using in vitro-to-in vivo extrapolation and reverse dosimetry.
Bioactivity quotients (BQs) are calculated as iR/OED to obtain estimates
of potential impact associated with each relevant use scenario. Of
the 180 chemicals considered, 38 had maximum iRs exceeding minimum
OEDs (i.e., BQs > 1). For most of these compounds, exposures are
associated
with direct intake, food/oral contact, or dermal exposure. The method
provides high-throughput estimates of exposure and important input
for decision makers to identify chemicals of concern for further evaluation
with additional information or more refined models