Concentrations and human health risk assessment of DDT and its metabolites in free-range and commercial chicken products from KwaZulu-Natal, South Africa

Dichlorodiphenyltrichloroethane for Malaria and Agricultural Uses and Its Impacts on Human Health

Pesticides are widely used in agriculture and disease control, and dichlorodiphenyltrichloroethane (DDT) is one of the most used pesticides in human history. Besides its significant contributions in pest control in agriculture, DDT was credited as having saved millions of human lives for controlling malaria and other deadly insect-transmitted diseases. Even today, the use of DDT in some countries for malaria control cannot be replaced without endangering people who live there. The recent COVID-19 pandemic has changed our lives and reminded us of the challenges in dealing with infectious diseases, especially deadly ones including malaria. However, DDT and its metabolites are stable, persist long, are found in almost every corner of the world, and their persistent effects on humans, animals, and the environment must be seriously considered. This review will focus on the history of DDT use for agriculture and malaria control, the pathways for the spread of DDT, benefits and risks of DDT use, DDT exposure to animals, humans, and the environment, and the associated human health risks. These knowledge and findings of DDT will benefit the selection and management of pesticides worldwide.

A lentic microcosm approach to determine the toxicity of DDT and deltamethrin on diatom communities

Worldwide the use of pesticides has increased, especially in the industry and agriculture sector even though they contain highly toxic substances. The use of pesticides has various negative effects on the aquatic ecosystem and organisms within these ecosystems. The paper aimed to assess the effects of increased concentrations of malaria vector control insecticides (Dichlorodiphenyltrichloroethane (DDT) and Deltamethrin (DTM)) on the freshwater diatom community structure using a microcosm approach as well as determine whether a mixture (DDT 1:1 Deltamethrin) exposure will have a greater influence on the diatom community when compared to single exposures of these insecticides. Diatoms were exposed to a high and low concentration (based on LC50 data for freshwater Xenopus laevis from the USEPA Ecotox database) of DDT, DTM and a mixture in lentic microcosms over a total period of 28 days. Results indicated that irrespective of exposure concentrations, DDT, DTM and a mixture had negative effects on the diatom community including functionality and vitality as these insecticides induced changes to their chloroplasts. There was an increased percentage dead cells for all exposures compared to the control, with the insecticides having a phototoxic effect on the diatom community. Exposure to the selected insecticides caused a significant decrease in some diatom metrics indicating the negative effects these insecticides have on the diatom metrics. Therefore, diatoms may prove to be useful as bio-indicators in ecotoxicology studies when assessing the effects of any insecticide exposures.

Exposure Routes and Health Risks Associated with Pesticide Application

Pesticides play an important role in agricultural development. However, pesticide application can result in both acute and chronic human toxicities, and the adverse effects of pesticides on the environment and human health remain a serious problem. There is therefore a need to discuss the application methods for pesticides, the routes of pesticide exposure, and the health risks posed by pesticide application. The health problems related to pesticide application and exposure in developing countries are of particular concern. The purpose of this paper is to provide scientific information for policymakers in order to allow the development of proper pesticide application technics and methods to minimize pesticide exposure and the adverse health effects on both applicators and communities. Studies indicate that there are four main pesticide application methods, including hydraulic spraying, backpack spraying, basal trunk spraying, and aerial spraying. Pesticide application methods are mainly selected by considering the habits of target pests, the characteristics of target sites, and the properties of pesticides. Humans are directly exposed to pesticides in occupational, agricultural, and household activities and are indirectly exposed to pesticides via environmental media, including air, water, soil, and food. Human exposure to pesticides occurs mainly through dermal, oral, and respiratory routes. People who are directly and/or indirectly exposed to pesticides may contract acute toxicity effects and chronic diseases. Although no segment of the general population is completely protected against exposure to pesticides and their potentially serious health effects, a disproportionate burden is shouldered by people in developing countries. Both deterministic and probabilistic human health risk assessments have their advantages and disadvantages and both types of methods should be comprehensively implemented in research on exposure and human health risk assessment. Equipment for appropriate pesticide application is important for application efficiency to minimize the loss of spray solution as well as reduce pesticide residuals in the environment and adverse human health effects due to over-spraying and residues. Policymakers should implement various useful measures, such as integrated pest management (IPM) laws that prohibit the use of pesticides with high risks and the development of a national implementation plan (NIP) to reduce the adverse effects of pesticides on the environment and on human health.

Regional Scale Risk to the Ecological Sustainability and Ecosystem Services of an African Floodplain System

The Phongolo floodplain is one of southern Africa's most important systems. In this study, we carried out a regional scale ecological risk assessment to evaluate the risk of multiple stressors associated with the use of the aquatic resources in the floodplain to selected social and ecological endpoints representing its sustainability. The floodplain has undergone significant changes as a result of the impacts of multiple stressors. This includes high risk of impact and threatened sustainability between the Pongolapoort Dam and the Ndumo Game Reserve (NGR). This compares to relatively low risk to the maintenance of the endpoints within the NGR. The reserve provides a protection and refuge function for regional biodiversity maintenance and ecosystem sustainability processes. In the study a range of scenarios were considered and demonstrate that the system will respond to protection measures and or increased resource use options. Should flood reductions or water quality pollution drivers continue on increasing trajectories, the condition of the Phongolo River and floodplain will probably deteriorate into an unacceptable, unsustainable state. Removal of the protection services of the NGR would result in an unsustainable ecosystem and loss of ecosystem services for regional vulnerable African communities. Additional evidence should be obtained from monitoring and research to refine, validate, and update the assessment in an adaptive management context. The risk assessment framework approach implemented in the Phongolo floodplain can contribute to the management of other floodplains ecosystems and the sustainability management of social and ecological attributes and processes of these important ecosystems.

Ten Bird Species, Six Guilds, Three Habitats, and 59 Chlorinated and Brominated POPs: What do 64 Eggs from the Largest Economic Hub of Southern Africa tell us?

There is little information on how POPs in eggs of different terrestrial, wetland, and aquatic birds share a large urban and rural landscape relate. We collected and analysed 64 eggs belonging to ten species of six feeding guilds, and compared organic chlorinated pesticide (OCP), polychlorinated biphenyl (PCB), and brominated flame retardants (BFR) residue concentrations and compositions. The eggs were collected in the Gauteng and the northern part of the Free Sate provinces of South Africa, one of the largest economic hubs in Africa. White-breasted Cormorant and African Darter eggs (at the highest trophic level as large aquatic predators) had the highest ΣOCP and ΣPCB concentrations, and Cape Sparrow and Southern Masked Weaver (granivores) eggs had the lowest concentrations, corresponding to the lowest trophic level in our collection. The highest percentage p,p'-DDT were in eggs of the terrestrial insectivore Crowned Lapwing (24%) and the scavenging African Sacred Ibis (17%), and the lowest in African Darter (1.0%) and White-breasted Cormorant (0.9%) eggs, suggesting that recency of DDT releases in a region cannot be gauged by this metric. African Sacred Ibis and Southern Masked Weaver eggs had the highest ΣBFR concentrations, with Crowned Lapwing, Cattle Egret, and White-breasted Cormorant eggs the least. Based on feeding guilds, the mean ΣPOP concentrations increased from granivore, aquatic omnivore, scavenger, terrestrial insectivore, small aquatic predator, to large aquatic predator. Mean ΣPOP concentrations in eggs increased from terrestrial, to wetland, to aquatic habitat birds. Interesting patterns were observed with multivariate analyses. There were no significant regressions between egg size and any summed POP classes. ΣBFR concentrations were not correlated with ΣOCPs or ΣPCBs. Eggshell thinning of African Darter eggs was associated with p,p'-DDE and ΣPCB suggesting risk. Other metrics also suggest risk. Therefore, different species of terrestrial and aquatic birds from the same area acquire and deposit POPs in different proportions and quantities in their eggs. Trophic levels and habitat explain the overall patterns, but detailed differences were found, some of which we are unable to explain. Based on POPs residues in terrestrial, wetland, and aquatic bird eggs, different POPs classes behave differently in a shared large inland industrial area, complicating deductions about POPs and associated risks based on one or few species.

The state of persistent organic pollutants in South African estuaries: A review of environmental exposure and sources

The long-term health of many South African estuaries is impacted by pollutants entering these systems through industrial and agricultural runoff, sewage outfalls, contaminated storm water drainage, flows from informal settlements, and plastic materials in marine debris. Uncontrolled inputs combined with poor environmental management often result in elevated levels of persistent organic pollutants (POPs) in affected estuaries. Data on POPs research from 1960 to 2020 were analysed in terms of their sources, environmental investigations, and health implications. The outcome showed polychlorinated biphenyls (PCBs) and per- and poly-fluoroalkyl sulphonates (PFASs) to exceed the US EPA health advisory levels for drinking water. Concentration of organochlorine pesticides (OCPs) in water were below the WHO limits, while those in fish tissues from most estuaries were found to be below the US FDA limits. Although environmental compartments in some estuaries (e.g. Rooiels and uMngeni estuaries) seem to be less contaminated relative to other marine systems around the world, many others were polluted and critically modified (e.g. Durban Bay, Swartkops, Sundays, and Buffalo systems). Due to inconsistent monitoring methods coupled with limited data availability, temporal trends were unclear. Of the 290 estuaries in South Africa, 65 were prioritised and recommended for POPs evaluation based on their pollution sources, and a monitoring strategy was defined in terms of sampling. Government policies to curb marine pollution need to be enforced to prevent chronic contamination that leads to water quality deterioration and loss of ecosystem services.

Bioaccumulation of DDT and other organochlorine pesticides in amphibians from two conservation areas within malaria risk regions of South Africa

The threat to wildlife from chemical exposure exists regardless of the presence of conservation boundaries. An issue exacerbated by the use of environmentally persistent insecticides for vector control and long-range transport of legacy persistent organic pollutants. In this comparative study between two important conservation regions in South Africa, Kruger National Park (KNP) and Ndumo Game Reserve (NGR), we assessed organochlorine pesticide (OCP) accumulation in several anuran species collected from within the conservation regions. The two conservation regions differ in size and subsequent proximity of collection sites to OCP input sources. Detectable concentrations of OCPs were present in ∼ half the frogs analysed from KNP and ∼all frogs from NGR and total OCP loads were similar between regions, where measured in the same species. The OCP profiles in KNP frogs were representative of legacy pesticides likely introduced via long-range transport, whereas NGR profiles showed influence of current use of DDT consistent with close proximity to sources. This indicates amphibians can accumulate OCPs within conservation regions and that the exposure of non-target organisms inside conservation regions to current use pesticides has a strong association with proximity to sources. These results serve to inform conservation management decision making with regard to the non-target organism effects of chemical interventions such as vector control pesticide use in and around conservation regions.

Contamination of Foods from Cameroon with Residues of 20 Halogenated Pesticides, and Health Risk of Adult Human Dietary Exposure

(1) Background: Halogenated pesticides are abundantly used in Cameroon, but there is no information on the health risk of consumers from exposure to their residues in foods. (2) Methods: Residues of 20 halogenated pesticides were determined in 11 agricultural products collected in the 3 largest cities of Cameroon using QuEChERS extraction and gas chromatography with electron capture detector (GC-ECD), and health risk from dietary exposure was assessed. (3) Results: Organochlorines pesticides aldrin, p,p'-dichlorodiphenyl-trichloroethane (DDT) and β-hexachlorocyclohexane (β-HCH) found in 85.0%, 81.9% and 72.5% of samples, respectively, were the most frequently detected. The highest average concentrations of residues were 1.12, 0.74 and 0.39 mg/kg for methoxychlor, alachlor and β-HCH, respectively, found in chilli pepper. Chili pepper (58.9%), cowpea (56.8%), black beans (56.5%) and kidney beans (54.0%) exhibited the highest residue occurrences. Levels above the European Union maximum residue limits (MRLs) were found for all the 20 pesticides, in 40.1% of the positive analyses, and the food samples contained 14 pesticides banned in Cameroon. Chronic, acute, cumulative and carcinogenic risk assessments revealed that lifetime consumption of maize, black beans, kidney beans, groundnuts and chili pepper contaminated with aldrin, dieldrin, endrin, HCB, heptachlor, o,p'-DDT, p,p'-DDD, p,p'-DDT, p,p'-DDE and β-HCH, could pose health risks. (4) Conclusion: These results show that there is an urgent need of pesticide usage regulation, effective application of pesticide bans and management of obsolete pesticide stocks in Cameroon.

Combined effect of microplastics and DDT on microbial growth: A bacteriological and metabolomics investigation in Escherichia coli

Microplastics (MPs) can adsorb toxic chemicals in biological or environmental matrixes and thus influence their behavior and availability. In order to investigate how the combined pollution of MPs and toxic organic chemical influence microbial growth and metabolism, Escherichia coli (E. coli) was grown in a complex, well-defined media and treated with polystyrene microplastics (PS MPs) and dichloro-diphenyl-tricgloroethane (DDT) at human relevant concentration levels. In vivo metabolites captured by a novel solid phase microextraction (SPME) probe, were used to reflect the metabolic dysregulation of E. coli under different pollution stresses. Results showed that the toxic effect of DDT displayed a distinct dose-dependent phenomenon while the existence of PS decreased the growth and metabolic interference effect of DDT on E. coli. Adsorption results revealed a mechanism that PS weakened the adverse impact of DDT by decreasing its free concentration in the treated culture media. Tricarboxylic acid (TCA) cycle related enzymes activities and antioxidant defense related substances of E. coli also proved the mechanism. The current study is believed to broaden our understanding of the ecotoxicity of MPs with toxic organic chemicals on microorganism.

Biomarker Responses in the Freshwater Shrimp Caridina nilotica as Indicators of Persistent Pollutant Exposure

Biomarkers are applied as early warning indicators of organisms' exposure to pollutants. The aim of this study was to utilise a multi-biomarker approach in the freshwater shrimp Caridina nilotica (Decapoda: Atyidae) as indicators of persistent pollutant exposure. A suite of biomarkers was selected to cover oxidative stress and damage, and energetics of the organisms. Five sites, representing an agricultural and pesticide application gradient, were sampled during two flow related hydro-periods in rivers of the Phongolo floodplain, north-eastern South Africa. Cytochrome P450 (CYP) activity was significantly higher in shrimp at sites directly adjacent to regions of increased human activity. Increased oxidative responses, i.e. catalase (CAT; p < 0.01) and protein carbonyl (PC, p < 0.01) were also found at these sites. The energetics biomarker did not show any influence of increased contaminant exposure. We demonstrated that the biomarkers of exposure (CYP) and effect (CAT, PC) were suitable to detect effects of stressors, probably persistent pollutants.

Occurrence and risk evaluation of organochlorine contaminants in surface water along the course of Swartkops and Sundays River Estuaries, Eastern Cape Province, South Africa

Organochlorine contaminants were analysed in surface water from Sundays (SDE) and Swartkops Estuaries (SWE), Eastern Cape Province, which is among the largest estuaries in South Africa. The concentration of Σ₁₈OCPs ranged from 16.7 to 249.2 ng/L in autumn, 19.9-81.4 ng/L in winter, 43.6-126.8 ng/L in spring and 68.3-199.9 ng/L in summer for SDE, whereas in SWE, the values varied from 20.9 to 259.7 ng/L in autumn, 58.9-263.9 ng/L in winter, 3.2-183.6 ng/L in spring and 118.0-188.9 ng/L in summer. Among all OCPs, α-HCH, β-HCH, p,p'-DDE, p,p'-DDT, endrin, dieldrin and endrin aldehyde were predominant in surface water samples from SDE and SWE. Furthermore, the mean concentration of polychlorinated biphenyls (PCBs) ranged from 126.7 ng/L in winter to 151.0 ng/L in spring for SDE and 249.0 ng/L in spring to 727.6 ng/L in winter for SWE. Tri- and tetra-PCBs dominated the PCB homologue profile. Hierarchical cluster analysis grouped the study sites into three regions from least polluted to most polluted, indicated that SWE is more polluted compared to SDE, probably due to the influx of agricultural and industrial effluents. Carcinogenic and non-carcinogenic risk assessment revealed that the water from both estuaries is not safe for drinking, although suitable for bathing.

Determinants of persistent organic pollutant (POP) concentrations in human breast milk of a cross-sectional sample of primiparous mothers in Belgium

BACKGROUND

Bio-accumulation of persistent organic pollutants (POPs) in the environment and in the food chain can lead to high pollutant concentrations in human fat-containing tissues and breast milk.

OBJECTIVES

We aimed to identify the maternal characteristics that determined POP concentrations in breast milk of primiparous mothers in Belgium.

METHODS

Breast milk samples were obtained from a cross-sectional sample of 206 primiparous mothers in 2014. POP concentrations in breast milk samples were determined by GC-ECNI-MS and GC-EI-MS/MS depending on the analytes' sensitivity. Associations between POP concentrations in breast milk and potential determinants were investigated using two-way contingency tables and multivariable generalized linear models.

RESULTS

Fifteen of the 23 screened POPs were detected in the breast milk samples. Four organochlorine compounds (p,p'-DDT, p,p'-DDE, HCB and β-HCH) and two brominated flame retardant congeners (BDE-47, BDE-153) were detected at concentrations above the limit of quantification in >50% of the breast milk samples. Maternal age and BMI were usually associated with higher POP concentrations. Rural residency and consumption of home-produced eggs, fatty fish and fish oil supplements were associated with higher concentrations of DDT and DDE. Consumption of fatty fish and being breastfed during childhood were associated with higher concentrations of HCB and β-HCH. Fish oil supplements and home-produced eggs were associated with higher concentrations of BDEs, but for BDE congeners exposure routes other than diet require further investigation.

CONCLUSIONS

Dietary and non-dietary determinants predict individual POP concentrations in breast milk.

Evidence of impacts from DDT in pelican, cormorant, stork, and egret eggs from KwaZulu-Natal, South Africa

DDT remains in use for malaria control in South Africa. We quantified DDTs in aquatic bird eggs from the highly biodiverse northern KwaZulu-Natal, a province of South Africa where DDT has been used for more than 80 years for malaria control. Pelican eggs had the highest ΣDDT concentration (7200 ng/g lipid mass; lm), Little Egret eggs had 6900 ΣDDT lm, African Openbill eggs had 3400 ng/g lm ΣDDT, and White-breasted Cormorant had 2400 ng/g lm. All species had non-significantly different mean concentrations of o,p'-DDT, p,p'-DDT, and ΣDDT, but with significant differences for p,p-DDE, o,p'-DDD, p,p'-DDD, %DDT, %DDD, and %lipid. The thinnest pelican eggshell (0.40 mm) had a ΣDDT concentration of 3300 ng/g lm.; the thickest shell (0.96 mm) had the lowest ΣDDT concentration at 29 ng/g lm; a 58% difference. Linear regressions of concentrations with shell thickness for the pelican eggs were significant for p,p'-DDE and p,p'-DDD, indicating risk of reproductive impairment. Compositional profiles indicate different food webs for the different species. DDT concentrations were lower than from another DDT-sprayed locality in South Africa, possible linked to differences in hydrology and rainfall. We conclude that significant ecotoxic threats associated with DDT remain in this area, and possibly threatens birds from less polluted areas. Our findings suggest continued negative human health and environmental impacts from DDT. There is an urgency to move away from DDT as quickly as possible; alternatively, to implement practices that prevent emissions of DDT to the environment while protecting human life.

Tuna byproducts as a fish-meal in tilapia aquaculture

Potentiality of the use of tuna byproducts as a fish-meal replacement on Nile tilapia (Oreochromis niloticus) was examined for 84 weeks by tracking the concentrations of cadmium and mercury in the internal organs, muscles and fish whole body through generation including their immature eggs and their larvae. The results confirmed that the tuna byproducts can be used as a fish-meal substitute in tilapia aquaculture, because their acceptable ranges for cadmium and mercury consequently did not exceed the food safety values (both < 0.5 mg kg^-1), despite their proportional increases in the fish body. The use of tuna byproducts as a protein source is expected to reduce the cost of feed with other fishmeal substitutes in tilapia aquaculture. However, fish (flounder) indiscriminately consuming tuna byproduct feed were prohibited and recalls of sales were issued by the government (July 2018, Republic of Korea), as the threshold for mercury in the fish bodies had been exceeded (0.6-0.8 mg kg^-1). Further study of the use of tuna byproducts as fishmeal replacements for other species in aquaculture is needed, as concentration ratios can vary depending on the species.

Environmental Chemical Contaminants in Food: Review of a Global Problem

Contamination by chemicals from the environment is a major global food safety issue, posing a serious threat to human health. These chemicals belong to many groups, including metals/metalloids, polycyclic aromatic hydrocarbons (PAHs), persistent organic pollutants (POPs), perfluorinated compounds (PFCs), pharmaceutical and personal care products (PPCPs), radioactive elements, electronic waste, plastics, and nanoparticles. Some of these occur naturally in the environment, whilst others are produced from anthropogenic sources. They may contaminate our food-crops, livestock, and seafood-and drinking water and exert adverse effects on our health. It is important to perform assessments of the associated potential risks. Monitoring contamination levels, enactment of control measures including remediation, and consideration of sociopolitical implications are vital to provide safer food globally.

Determination of selected endocrine disruptors in organic, free-range, and battery-produced hen eggs and risk assessment

An increasing amount of evidence suggests that phthalic acid esters (PAE), polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE), and organochlorine pesticides (OCP) are related to mutagenic, carcinogenic, and endocrine disruptor effects (EDCs). These lipophilic compounds are highly resistant to breakdown processes, and consequently remain in the environment, followed by uptake into the food chain. Human exposure to lipophilic compounds results from the consumption of food containing EDCs, mainly foodstuffs of animal origin with a high fat content, since these contaminants accumulate in fatty tissues. Foodstuffs in which EDCs can accumulate include meat, fish, eggs, and milk. We investigated the contamination in edible eggs to determine whether relative differences in the contaminants' residue levels appeared in three types of egg production (i.e., battery, free-range, and organic). The results showed that PAEs, especially dimethyl phthalate contamination, was the most abundant in the battery eggs, and the PCBs, PBDEs, and OCPs were the most abundant in the free-range eggs. The eggs were contaminated by more than one chemical, and as many as five contaminants (PCB180, PBDE47, dimethyl phthalate, diethyl phthalate, and di-n-butyl phthalate in battery eggs, and PCB138, PCB153, PCB180, diethyl phthalate, and di-2-ethylhexyl phthalate in organic eggs) were detected in the same egg. However, none of the chemicals detected were at the maximum limit of acceptable risk.

Linking organochlorine exposure to biomarker response patterns in Anurans: a case study of Müller's clawed frog (Xenopus muelleri) from a tropical malaria vector control region

Organochlorine pesticides are highly persistent in aquatic ecosystems. Amphibians, specifically anurans, play an intricate part in the aquatic food web, and have very permeable skin which makes them prone to bioaccumulation of persistent pollutants. In this study the bioaccumulation of various legacy organochlorine pesticides (OCPs)-including dichlorodiphenyltrichloroethane (DDT), currently used for malaria vector control (MVC)-was assessed along with a set of biomarker responses in Müller's clawed frog Xenopus muelleri collected from the lower Phongolo River floodplain in South Africa. Possible relationships between bioaccumulation and biomarkers (of exposure, oxidative stress biomarkers, and cellular energy allocation) alongside their temporal changes were investigated. The OCP concentrations showed a significant increase over time for the duration of the study. The increase correlated negatively with rainfall from the region. DDT levels were well below expected effects levels with p,p-DDE being the main contributing metabolite. The results of this study indicate OCPs actively accumulate at sub-lethal levels in aquatic frogs from the study area, while showing possible relations towards some of the biochemical stress responses measured. Most notable were negative relationships indicated between p,p-DDE and acetylcholinesterase, malondialdehyde, and carbohydrates and protein energy availability. Levels of DDT were not found to be significantly higher than other legacy pesticides in the frog tissue, although evidence of newly introduced DDT in the frog tissue was found. Further investigation about sub-lethal effects of these pesticides on anurans is required to gain better insight into their full impact on animal livelihood.

Investigation of mRNA expression changes associated with field exposure to DDTs in chickens from KwaZulu-Natal, South Africa

The objective of this study was to identify potential mRNA expression changes in chicken livers associated with environmental exposure to dichloro-diphenyl-trichloroethane (DDT) and its metabolites (DDTs). In particular, we focused on genes relating to the immune system and metabolism. We analyzed liver samples from free-ranging chickens in KwaZulu-Natal, South Africa, for contamination by DDTs. This area predominantly uses DDT in its malaria control program, and homes are sprayed annually with the pesticide. Genes relating to the immune system and metabolism were selected as potential genetic biomarkers that could be linked to higher contamination with DDTs. RT-qPCR analysis on 39 samples showed strong correlations between DDTs contamination and mRNA expression for the following genes: AvBD1, AvBD2, AvBD6 and AvBD7 (down-regulated), and CYP17, ELOVL2 and SQLE (up-regulated). This study shows for the first time interesting and significant correlations between genetic material collected from environmentally-exposed chickens and mRNA expression of several genes involved in immunity and metabolism. These findings show the usefulness of analysis on field samples from a region with high levels of environmental contamination in detecting potential biomarkers of exposure. In particular, we observed clear effects from DDT contamination on mRNA expression of genes involved in immune suppression, endocrine-disrupting effects, and lipid dysregulation. These results are of interest in guiding future studies to further elucidate the pathways involved in and clinical importance of toxicity associated with DDT exposure from contaminated environments, to ascertain the health risk to livestock and any subsequent risks to food security for people.