Allergic reaction induced by dermal and/or respiratory exposure to low-dose phenoxyacetic acid, organophosphorus, and carbamate pesticides

Immunotoxicity In Vitro Assays for Environmental Pollutants under Paradigm Shift in Toxicity Tests

With the outbreak of COVID-19, increasingly more attention has been paid to the effects of environmental factors on the immune system of organisms, because environmental pollutants may act in synergy with viruses by affecting the immunity of organisms. The immune system is a developing defense system formed by all metazoans in the course of struggling with various internal and external factors, whose damage may lead to increased susceptibility to pathogens and diseases. Due to a greater vulnerability of the immune system, immunotoxicity has the potential to be the early event of other toxic effects, and should be incorporated into environmental risk assessment. However, compared with other toxicity endpoints, e.g., genotoxicity, endocrine toxicity, or developmental toxicity, there are many challenges for the immunotoxicity test of environmental pollutants; this is due to the lack of detailed mechanisms of action and reliable assay methods. In addition, with the strong appeal for animal-free experiments, there has been a significant shift in the toxicity test paradigm, from traditional animal experiments to high-throughput in vitro assays that rely on cell lines. Therefore, there is an urgent need to build high-though put immunotoxicity test methods to screen massive environmental pollutants. This paper reviews the common methods of immunotoxicity assays, including assays for direct immunotoxicity and skin sensitization. Direct immunotoxicity mainly refers to immunosuppression, for which the assays mostly use mixed immune cells or isolated single cells from animals with obvious problems, such as high cost, complex experimental operation, strong variability and so on. Meanwhile, there have been no stable and standard cell lines targeting immune functions developed for high-throughput tests. Compared with direct immunotoxicity, skin sensitizer screening has developed relatively mature in vitro assay methods based on an adverse outcome pathway (AOP), which points out the way forward for the paradigm shift in toxicity tests. According to the experience of skin sensitizer screening, this paper proposes that we also should seek appropriate nodes and establish more complete AOPs for immunosuppression and other immune-mediated diseases. Then, effective in vitro immunotoxicity assay methods can be developed targeting key events, simultaneously coordinating the studies of the chemical immunotoxicity mechanism, and further promoting the paradigm shift in the immunotoxicity test.

Allergy from perspective of environmental pollution effects: from an aspect of atopic dermatitis, immune system, and atmospheric hazards-a narrative review of current evidences

Environmental pollution has become more diversified in recent years as technologies for urbanization is increasingly more advanced. Several environmental factors such as air and water pollutants have been linked to allergic symptoms. For instance, because of industrialization for city development in many countries, polluted soil or tiny particles in the air could result in an even more hazardous environment for people to reside. Aside from the aspects of environmental issues, other newly emerging factors such as the electromagnetic field (EMF) also require further investigation. Here, in this narrative review, we focused on allergens from atmospheric and water pollution, hygiene improvement, changes in food trend, and residential environmental pollution. Current evidences regarding the association between various pollutants and the potential clinical diseases could be induced. For people with high skin exposure to air pollutants such as PM 2.5, PM 10, or sulfur dioxide, potential onset of dermatological allergic events should be alerted. The mechanisms involved in allergic diseases are being discussed and summarized. Interactions between immunological mechanisms and clinical implications could potentially provide clearer view to the association between allergic status and pollutants. Moreover, understanding the mechanistic role of allergens can raise awareness to global environment and public health.

Differential immunomodulatory effects of six pesticides of different chemical classes on human monocyte-derived macrophage functions

Exposure to pesticides through eyes, skin, ingestion and inhalation may affects human health by interfering with immune cells, such as macrophages. We evaluated, in vitro, the effect of six pesticides widely used in apple arboriculture on the functions of human monocyte-derived macrophages (hMDMs). hMDMs were cultured for 4 or 24 h with or without pesticides (0.01, 0.1, 1, 10 μmol.L^-1). We showed that chlorpyrifos, thiacloprid, thiophanate, boscalid, and captan had little toxic effect at the tested concentrations, while dithianon had low-cytotoxicity at 10 μmol.L^-1. While boscalid showed no effect on hMDMs function, thiophanate (0.01 μmol.L^-1) stimulated with TPA and thiacloprid (1, 10 μmol.L^-1) stimulated with zymosan activated ROS production. Chlorpyrifos, dithianon, and captan inhibited ROS production and TNF-α, IL-1β pro-inflammatory cytokines. We established that dithianon (0.01-1 μmol.L^-1) and captan (0.1, 1 μmol.L^-1) induced mRNA expression of NQO1 and HMOX1 antioxidant enzymes. Dithianon also induced the mRNA expression of catalase, superoxide dismutase-2 at 10 μmol.L^-1. Together, these results show that exposure to chlorpyrifos, dithianon, and captan induce immunomodulatory effects that may influence the disease fighting properties of monocytes/macrophages while pesticides such as thiacloprid, thiophanate and boscalid have little influence.

Subchronic exposure to a glyphosate-based herbicide causes dysplasia in the digestive tract of Wistar rats

Glyphosate-based herbicides (GBH) are the most widely used herbicide for treatment of crops in the world. The digestive tract is one of the first systems exposed to pesticides, and damage to this system can affect the general health of individuals. The aim of this study was to evaluate the effects of subchronic inhalation and oral exposure to GBH on the digestive tract in rats. Six groups of Wistar rats (male and female) were exposed to nebulization with three concentrations of GBH [3.71 × 10-3 grams of active ingredient per hectare (g.a.i./ha), 6.19 × 10-3 g.a.i./ha and 9.28 × 10-3 g.a.i./ha] administered orally or by inhalation for 75 days. Bone marrow cells, smears of the tongue and fragments of the tongue, oesophagus, stomach and intestine were collected for histopathological analysis. Congestion, inflammation, an increase in the number of mast cells and nucleoli-organizing regions were detected in the tongue in the groups exposed to GBH. Females had a higher number of mast cells in the tongue than males. Animals in the groups exposed to higher concentrations of GBH showed dysplasia in the oesophagus and small and large intestine regardless of sex. Gastric changes were not observed. Animals exposed to GBH showed increased micronucleus formation. Our data indicate that GBH causes oral allergies and dysplastic lesions in the oesophagus and small and large intestine and has genotoxic potential.

Evaluation of the potential teratogenic and toxic effect of the herbicide 2,4-D (DMA® 806) in bullfrog embryos and tadpoles (Lithobates catesbeianus)

The objective of this work was to evaluate the potential teratogenic and toxic effect of the herbicide 2,4-D (DMA® 806) on bullfrog embryos and tadpoles (Lithobates catesbeianus). We used the FETAX (Frog Embryo Teratogenesis Assay Xenopus) assay for embryos, and for tadpoles, we used acute (96 h) and chronic (49 days) toxicity tests and evaluated aspects of healthiness, hematology, and histopathology. The LC_50-144h (Median Lethal Concentration), EC_50-144h (Median Effective Concentration), MCIG (Minimum Concentration to Inhibit Growth) and TI (Teratogenic Index) for embryos were 792 mg/L, 593 mg/L, 150 mg/L of 2,4-D (DMA) and 1.34, respectively. For tadpoles, the LC_50-96h was 700 mg/L of 2,4-D (DMA) and chronic test indicated an inflammatory process and erythrocytosis (with possible polycythemia), with consequent reduction of the spleen. This demonstrates physiological stress probably due to dehydration, which can be proven by the gill tufts widening intercellular space and gill tuft fusions. We also found injuries to the kidneys and skin of the animals even in the lowest concentration tested. Our results indicated that this pesticide is minimally teratogenic and has a low toxicity on L. catesbeianus embryos and tadpoles, but it can inhibit embryo growth in concentrations lower than those tested in this study. We hypothesized that the herbicide 2,4-D (DMA® 806) may be a respiratory allergen for L. catesbeianus tadpoles and recommend precautionary measures for prolonged exposure of aquatic organisms to this pesticide.

Oral mucosa changes associated with chronic oral and inhalation exposure to 2,4-dichlorophenoxiacetic acid (2,4-D) in Wistar rats

The respiratory tract and the oral mucosa are the first areas contaminated by pesticides. The herbicide dichlorophenoxyacetic acid (2,4-D) is a widely used pesticide across the world for both crops and gardens. The aim of this study was to evaluate oral mucosal damage after an experimental simulation of chronic oral and inhalational environmental exposure to 2,4-D formulation. Eighty male Wistar rats were exposed to three distinct concentrations of 2,4-D formulation (low-187.17 mg/m3; medium-313.31 mg/m3; and high-467.93 mg/m3). Oral exposure (through contaminated feed) or inhalation exposure lasted 6 months. Rat tongues were collected for cyto- and histopathology. There was a difference between exposure groups in the intensity of tissue congestion. Most rats exposed to 2,4-D presented mucosal inflammation at both cytology and histology (P < 0.05). Hyperkeratosis only occurred in rats exposed orally at the high concentration. There was an increase in the number of nucleoli-organizing regions in the dorsal epithelium as the 2,4-D concentration increased (P < 0.001). The inhalation route was more associated with increased mitosis figures and nucleoli-organizing region count (P < 0.05). Chronic oral and inhalation exposure to high concentrations of 2,4-D formulation caused an increase in the proliferation rate and thickness of the tongue epithelium and stimulated the inflammatory response in the tissue.

Evaluation of buccal damage associated with acute inhalation exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) in mice

BACKGROUND

The herbicide dichlorophenoxyacetic acid (2,4-D) is one of the most widely used crop spraying products in the world. Some pesticides induce the degranulation of mast cells and increase allergic responses. This is the first study to evaluate the damage to the oral mucosa after an experimental simulation of environmental inhalation exposure to the 2,4-D herbicide. The aim of this study was evaluate the possible oral damage caused by acute inhalation exposure to the herbicide 2,4-D.

RESULTS

There was a difference between the exposure concentrations in relation to tissue congestion intensity (p = 0.002) and mast cell counts (p = 0.002), a difference in the evaluation of the interaction between the exposure concentrations and nebulization time in the dorsum epithelium thickness (p = 0.013), and a significant correlation between the epithelial thickness and the number of nucleoli organizing regions on the dorsum of the tongue (p = 0.048).

CONCLUSIONS

Even after acute exposure, the herbicide 2,4-D had the potential to damage the oral epithelium, especially at higher doses.

Acute respiratory symptoms and its associated factors among mothers who have under five-years-old children in northwest, Ethiopia

Background

Poor air quality of the household is likely to be the largest public health concern in resource-constrained countries. Exposure to household air pollution, poor working environment, and fuel type used at household level have been associated with respiratory symptoms. This study aimed to assess acute respiratory symptoms and its associated factors among mothers who have under five-years-old children in Gondar city, northwest Ethiopia.

Method

A cross-sectional study was carried out from February 15, 2019 to June 20, 2019. Study participants were selected using simple random sampling, and data were collected via face-to-face interviews. Binary logistic regression analysis was used to test the association of explanatory and outcome variables. Variables with p < 0.05 were considered as significantly associated with the outcome variable.

Results

The prevalence of respiratory symptoms among mothers of under-five years-old children in this study was 46.1%. Education (vocational training compared to cannot read and write) (adjusted odd ratio (AOR) = 0.26 at 95% confidence interval (CI): 0.08–0.82), working in dusty environment (AOR = 2.90 at 95% CI: 1.39–6.08), wood fire use (AOR = 0.37 at 95% CI: 0.16–0.85), living in mud- and wood-walled houses (AOR = 0.53 at CI: 0.32–0.89), recent house painting (AOR = 1.95 at 95% CI: 1.03–3.69), new carpet (AOR = 2.02 at 95% CI: 1.08–3.77), pesticide use (AOR = 1.71 at 95% CI: 1.03–2.84), damp stain (AOR = 2.45 at 95% CI: 1.04–5.75), spending longer time in house for 6 to 11 h (AOR = 2.59 at 95% CI: 1.53–4.37) and 11 to 15 h (AOR = 3.47 at 95% CI: 1.87–6.43), and living less than 100 m from unpaved roads/streets (AOR = 4.35 at 95% CI: 2.64–7.18) were significantly associated with respiratory symptoms among mothers of under-five years-old children.

Conclusion

Respiratory symptoms were common among mothers who have under five-years-old children. Air quality improvement, fuel selection, and residential planning will help to reduce respiratory symptoms.

Mechanisms of organophosphorus pesticide toxicity in the context of airway hyperreactivity and asthma

Numerous epidemiologic studies have identified an association between occupational exposures to organophosphorus pesticides (OPs) and asthma or asthmatic symptoms in adults. Emerging epidemiologic data suggest that environmentally relevant levels of OPs may also be linked to respiratory dysfunction in the general population and that in utero and/or early life exposures to environmental OPs may increase risk for childhood asthma. In support of a causal link between OPs and asthma, experimental evidence demonstrates that occupationally and environmentally relevant OP exposures induce bronchospasm and airway hyperreactivity in preclinical models. Mechanistic studies have identified blockade of autoinhibitory M2 muscarinic receptors on parasympathetic nerves that innervate airway smooth muscle as one mechanism by which OPs induce airway hyperreactivity, but significant questions remain regarding the mechanism(s) by which OPs cause neuronal M2 receptor dysfunction and, more generally, how OPs cause persistent asthma, especially after developmental exposures. The goals of this review are to 1) summarize current understanding of OPs in asthma; 2) discuss mechanisms of OP neurotoxicity and immunotoxicity that warrant consideration in the context of OP-induced airway hyperreactivity and asthma, specifically, inflammatory responses, oxidative stress, neural plasticity, and neurogenic inflammation; and 3) identify critical data gaps that need to be addressed in order to better protect adults and children against the harmful respiratory effects of low-level OP exposures.

Pesticides are Associated with Allergic and Non-Allergic Wheeze among Male Farmers

BACKGROUND

Growing evidence suggests that pesticide use may contribute to respiratory symptoms.

OBJECTIVE

We evaluated the association of currently used pesticides with allergic and non-allergic wheeze among male farmers.

METHODS

Using the 2005-2010 interview data of the Agricultural Health Study, a prospective study of farmers in North Carolina and Iowa, we evaluated the association between allergic and non-allergic wheeze and self-reported use of 78 specific pesticides, reported by ≥ 1% of the 22,134 men interviewed. We used polytomous regression models adjusted for age, BMI, state, smoking, and current asthma, as well as for days applying pesticides and days driving diesel tractors. We defined allergic wheeze as reporting both wheeze and doctor-diagnosed hay fever (n = 1,310, 6%) and non-allergic wheeze as reporting wheeze but not hay fever (n = 3,939, 18%); men without wheeze were the referent.

RESULTS

In models evaluating current use of specific pesticides, 19 pesticides were significantly associated (p < 0.05) with allergic wheeze (18 positive, 1 negative) and 21 pesticides with non-allergic wheeze (19 positive, 2 negative); 11 pesticides were associated with both. Seven pesticides (herbicides: 2,4-D and simazine; insecticides: carbaryl, dimethoate, disulfoton, and zeta-cypermethrin; and fungicide pyraclostrobin) had significantly different associations for allergic and non-allergic wheeze. In exposure-response models with up to five exposure categories, we saw evidence of an exposure-response relationship for several pesticides including the commonly used herbicides 2,4-D and glyphosate, the insecticides permethrin and carbaryl, and the rodenticide warfarin.

CONCLUSIONS

These results for farmers implicate several pesticides that are commonly used in agricultural and residential settings with adverse respiratory effects.

From immunotoxicity to carcinogenicity: the effects of carbamate pesticides on the immune system

The immune system can be the target of many chemicals, with potentially severe adverse effects on the host's health. In the literature, carbamate (CM) pesticides have been implicated in the increasing prevalence of diseases associated with alterations of the immune response, such as hypersensitivity reactions, some autoimmune diseases and cancers. CMs may initiate, facilitate, or exacerbate pathological immune processes, resulting in immunotoxicity by induction of mutations in genes coding for immunoregulatory factors and modifying immune tolerance. In the present study, direct immunotoxicity, endocrine disruption and inhibition of esterases activities have been introduced as the main mechanisms of CMs-induced immune dysregulation. Moreover, the evidence on the relationship between CM pesticide exposure, dysregulation of the immune system and predisposition to different types of cancers, allergies, autoimmune and infectious diseases is criticized. In addition, in this review, we will discuss the relationship between immunotoxicity and cancer, and the advances made toward understanding the basis of cancer immune evasion.

Effect of pesticide exposure on immunological, hematological and biochemical parameters in thai orchid farmers- a cross-sectional study

Various studies have found that many Thai orchid farmers used excessive amounts of pesticides without proper protective gear, but no toxicological study has been made. This cross-sectional study aimed to evaluate the immunological, hematological and biochemical statuses of these farmers. Sixty four orchid farmers and 60 controls were studied. Plasma cholinesterase activity, the percentage and absolute number of B lymphocytes (CD19+) were significantly lower in the farmers group (3966.32±1165.48 U/L, 11.61±4.09% and 312.26±164.83 cells/mm3, respectively) as compared to those of controls (5048.85±1139.40 U/L, 14.32±4.23%, 420.34±195.18 cells/mm3, respectively). There was a statistically significant higher level of serum IgE among the orchid farmers (0.031±0.011 mg/dL vs. 0.018±0.007 mg/dL) but not IgG, IgA and IgM, levels. Serum lysozyme level, lymphocyte proliferative responses to mitogens, hematological parameters and kidney function test, were not significantly different between the two groups. The liver function profiles showed significantly lower levels of albumin and serum protein in the farmer group. Thus frequent pesticide exposure resulted in subtle changes of some biological parameters. These changes, though may not be clinically significant, strongly indicated that caution in handing pesticides by these farmers is warranted.

Allergic diseases and risk of hematopoietic malignancies in a cohort of postmenopausal women: a report from the Iowa Women's Health Study

BACKGROUND

Allergic diseases signify immune dysregulation attributable to underlying genetics and environmental exposures. Associations between various allergies and hematopoietic cancers have been observed, albeit inconsistently; however, few prospective studies have examined the risk, and even fewer among older adults.

METHODS

We examined risk of incident hematopoietic cancers in those reporting allergic diseases in a population-based cohort of 22,601 older women (Iowa Women's Health Study). Self-reported allergic status, including asthma, hay fever, eczema, and/or other allergies, was determined via questionnaire in 1997 (mean age, 72 years; range, 63-81 years). Incident cancers were ascertained by linkage with the Iowa Cancer Registry from 1997 to 2011. Cox proportional hazards regression was performed to estimate multivariate-adjusted HR and 95% confidence intervals (CI) for myeloid (N = 177) and lymphoid (N = 437) malignancies, respectively.

RESULTS

Allergic diseases were not associated with risk of myeloid (HR, 1.00; 95% CI, 0.72-1.37) or lymphoid (HR, 0.99; 95% CI, 0.81-1.22) malignancies overall, or for most allergic and malignant subtypes examined. Self-reported asthma was positively associated with development of myelodysplastic syndrome (MDS; HR, 2.00; 95% CI, 0.93-4.32). In addition, there was a 30% to 40% decrease in risk of both lymphoid and myeloid cancers in those reporting rural residences but no association in those reporting urban residences; the interaction between residence and allergy was statistically significant for lymphoid malignancies (Pinteraction = 0.05).

CONCLUSIONS AND IMPACT

These results suggest that asthma may contribute to the pathogenesis of MDS, a finding consistent with the chronic antigen stimulation hypothesis. Susceptibility differences by location of residence are concordant with the hygiene hypothesis and merit additional exploration.

Analysis of the molecular structure and vibrational spectra of the indole based analgesic drug indomethacin

The stability of the syn and anti structures of the non-steroidal anti-inflammatory drug indomethacin were investigated by the DFT-B3LYP and ab initio MP2 calculations with the 6-311G(**) basis set. The molecule was predicted at the DFT and MP2 levels of calculation to have the syn (C1N7C10C18 ∼40°) form being about 1.7 and 1.5kcal/mol, respectively lower in energy than the anti (C1N7C10C18 ∼140°) structure. The calculated CNCC torsional angles for the chlorobenzene and indole rings syn-anti conformational interconversion was in a good qualitative agreement with the reported X-ray angles (C1N7C10C18 ∼29 and 155°) for the syn and anti conformers, respectively). Indomethacin was estimated from the calculated Gibb's free energies to have an equilibrium mixture of 95% syn and 5% anti structures at 298.15K. The vibrational wavenumbers were computed at the B3LYP level of theory and complete vibrational assignments were provided on the basis of theoretical and normal coordinate calculations combined with experimental infrared and Raman data of the molecule. The analysis of the observed spectra supports the presence of indomethacin in only one conformation at room temperature.

Residential pesticide use is associated with children's respiratory symptoms

OBJECTIVE

To characterize the association between residential pesticide application and acute and chronic respiratory symptoms in children, focusing on the location of the pesticide application in and around the home and the type of pesticide applicator (professional vs nonprofessional).

METHODS

We used 1999 to 2004 National Health and Nutrition Examination Survey results to investigate this association in children younger than 18 years (N = 14,065).

RESULTS

Overall, pesticide use in the home was not associated with wheezing (odds ratio [OR], 1.15; 95% confidence interval [CI], 0.91 to 1.47). Nevertheless, pesticide use in the kitchen or dining rooms was significantly associated with increased odds of wheezing (OR, 1.39; 95% CI, 1.08 to 1.78) and dry cough (OR, 2.38; 95% CI, 1.40 to 4.06) after controlling for covariates.

CONCLUSIONS

These findings suggest that residential use of pesticides and the location of pesticide application are associated with increased respiratory complaints in children.

Effect of agropesticides use on male reproductive function: a study on farmers in Djutitsa (Cameroon)

This study aimed at investigating the effect of agropesticides on male reproductive function in farmers in Djutitsa (West Cameroon). To this end, 47 farmers in Djutitsa were asked questions on their health status and pesticide use in agriculture. Thereafter, their blood samples were collected for assessment of sex hormones including serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), androstenedione, testosterone, as well as sex hormone binding globulin (SHBG). Their serum triiodothyronine (T3) and thyroxine (T4) levels were also measured. Thirty seven men not exposed to agropesticides were recruited as control group. Fifty six pesticides containing 25 active substances were currently used by farmers enrolled in our study, and most of their symptoms were related to spread/use of these chemicals. Compared to the control group, there was no significant difference in FSH, LH, SHBG, estradiol, and thyroid hormones (T3 and T4) levels. Farmers had significantly lower serum testosterone (20.93 ± 1.03 nM vs. 24.32 ± 1.32 nM; P < 0.05) and higher androstenedione level (3.83 ± 0.20 nM vs. 2.80 ± 0.15 nM; P < 0.001). Their serum free testosterone as well as bioavailable testosterone were unchanged, while estradiol/testosterone and androstenedione/testosterone ratios were significantly increased (0.45 ± 0.03% vs. 0.33 ± 0.02%; P < 0.01 and 12.26 ± 3.64 vs 19.31 ± 6.82; P < 0.001, respectively). Our results suggest that male farmers of Djutitsa (West Cameroon) are exposed to agropesticides due to improper protective tool, and this exposure may impair their reproductive function through inhibition of testosterone synthesis; probably by inhibition of testicular 17β- hydroxysteroid dehydrogenase (17HSD3) and induction of aromatase (CYP19).

Pesticides and asthma

PURPOSE OF REVIEW

Several clinical and epidemiological studies have reported an association between exposure to pesticides, bronchial hyper-reactivity and asthma symptoms. This article reviews the mechanistic evidence lending support to the concept that either acute or chronic low-level inhalation of pesticides may trigger asthma attacks, exacerbate asthma or increase the risk of developing asthma.

RECENT FINDINGS

Pesticide aerosols or gases, like other respiratory irritants, can lead to asthma through interaction with functional irritant receptors in the airway and promoting neurogenic inflammation. Cross-talk between airway nerves and inflammatory cells helps to maintain chronic inflammation that eventually damages the bronchial epithelium. Certain organophosphorus insecticides cause airway hyper-reactivity via a common mechanism of disrupting negative feedback control of cholinergic regulation in the lungs. These pesticides may interact synergistically with allergen sensitization rendering individuals more susceptible for developing asthma.

SUMMARY

Many pesticides are sensitizers or irritants capable of directly damaging the bronchial mucosa, thus making the airway very sensitive to allergens or other stimuli. However, most pesticides are weakly immunogenic so that their potential to sensitize airways in exposed populations is limited. Pesticides may increase the risk of developing asthma, exacerbate a previous asthmatic condition or even trigger asthma attacks by increasing bronchial hyper-responsiveness.

Irritancy and allergic responses induced by topical application of ortho-phthalaldehyde

Although ortho-phthalaldehyde (OPA) has been suggested as an alternative to glutaraldehyde for the sterilization and disinfection of hospital equipment, the toxicity has not been thoroughly investigated. The purpose of these studies was to evaluate the irritancy and sensitization potential of OPA. The EpiDerm Skin Irritation Test was used to evaluate in vitro irritancy potential of OPA and glutaraldehyde. Treatment with 0.4125 and 0.55% OPA induced irritation, while glutaraldehyde exposure at these concentrations did not. Consistent with the in vitro results, OPA induced irritancy, evaluated by ear swelling, when mice were treated with 0.75%. Initial evaluation of the sensitization potential was conducted using the local lymph node assay at concentrations ranging from 0.005 to 0.75%. A concentration-dependent increase in lymphocyte proliferation was observed with a calculated EC3 value of 0.051% compared to that of 0.089%, previously determined for glutaraldehyde. Immunoglobulin (Ig) E-inducing potential was evaluated by phenotypic analysis of draining lymph node (DLN) cells and measurement of total and specific serum IgE levels. The 0.1 and 0.75% exposed groups yielded significant increases in the IgE+B220+ cell population in the lymph nodes while the 0.75% treated group demonstrated significant increases in total IgE, OPA-specific IgE, and OPA-specific IgG(1). In addition, significant increases in interleukin-4 messenger RNA and protein expression in the DLNs were observed in OPA-treated groups. The results demonstrate the dermal irritancy and allergic potential of OPA and raise concern about the proposed/intended use of OPA as a safe alternative to glutaraldehyde.