Thermal stress and the physiological response to environmental toxicants

Hypothermia as potential therapeutic approach to attenuating soman-induced seizure, neuropathology, and mortality with an adenosine A1 receptor agonist and body cooling

Organophosphorus nerve agents, such as soman (GD), produce excitotoxic effects resulting in sustained status epilepticus (SSE) and brain damage. Previous work shows that neuronal inhibitory effects of A1 adenosine receptor (A1AR) agonists, such as N6- Bicyclo (2.2.1)-hept-2-yl-5'-chloro-5'-deoxyadenosine (Cl-ENBA), suppresses GD-induced SSE and improves neuropathology. Some other physiologic effects of these agonists are hypothermia, hypotension, and sedation. Hypothermia may also shield the brain from injury by slowing down chemical insults, lessening inflammation, and contributing to improved neurological outcomes. Therefore, we attempted to isolate the hypothermic effect from ENBA by assessing the neuroprotective efficacy of direct surface body cooling in a rat GD-induced SSE model, and comparing the effects on seizure termination, neuropathology, and survival. Male rats implanted with a body temperature (Tb) transponder and electroencephalographic (EEG) electrodes were primed with asoxime (HI-6), exposed to GD 30 min later, and then treated with Cl-ENBA or had Tb lowered directly via body cooling at 30 min after the onset of seizure activity. Afterwards, they were either allowed to develop hypothermia as expected, or received thermal support to maintain normothermic Tb for a period of 6-h. Neuropathology was assessed at 24 h. Regardless of Cl-ENBA or surface cooling, all hypothermic GD-exposed groups had significantly improved 24-h survival compared to rats with normothermic Tb (81% vs. 39%, p < 0.001). Cl-ENBA offered neuroprotection independently of hypothermic Tb. While hypothermia enhanced the overall efficacy of Cl-ENBA by improving survival outcomes, body cooling didn't reduce seizure activity or neuropathology following GD-induced SSE.

Temperature modifies the effects of air pollutants on respiratory diseases

Increasing studies have reported temperature modification effects on air pollutants-induced respiratory diseases. In the current study, daily data of respiratory emergency room visits (ERVs), meteorological factors, and concentrations of air pollutants were collected from 2013 to 2016 in Lanzhou, a northwest city in China. Daily average temperature was stratified into low (≤ 25 percentile, P₂₅), medium (25-75 percentile, P₂₅-P₇₅) and high (≥ 75 percentile, P₇₅) to explore how temperature modifies the effects of air pollutants (PM_2.5, PM₁₀, SO₂, and NO₂) on respiratory ERVs by using generalized additive Poisson regression model (GAM). Seasonal modification was also investigated. Results showed that (a) PM₁₀, PM_2.5, and NO₂ had the strongest effects on respiratory ERVs in low temperature; (b) males and 15-and-younger were more vulnerable in low temperature while females and those older than 46 years were highly affected in high temperature; (c) PM₁₀, PM_2.5, and NO₂ were mostly associated with the total and both males and females in winter, while SO₂ resulted in the highest risk for the total and males in autumn and females in spring. In conclusion, this study found significant temperature modification effects and seasonal differences on the risks of respiratory ERVs due to air pollutants in Lanzhou, China.

Heat Stress and Cardiac Strain in French Vineyard Workers

Agricultural workers often produce considerable excess heat due to the physically demanding nature of their activities, increasing their risk of thermal stress in even moderately warm conditions. Few studies have examined the physiological responses to heat load in agriculture. We aimed to assess the heat strain experienced by vineyard workers during canopy management in dry field conditions, and to disentangle the effects of the heat produced by the body and the thermal environment. Thirty workers from five Bordeaux vineyards of southern France were monitored during vine-lifting and trellising (June 2012). The mean heart rate, net cardiac cost, relative cardiac cost, and cardiac workload score were assessed during field activity. As the workers were nested within vineyards, multilevel linear regression models were used for correct inference. Skin temperature increased by an average of 1.0°C. Cardiac indices showed marked differences between individuals. The workload was evaluated as 'heavy' or 'very heavy' for more than one-third of the workers, of whom one experienced heat exhaustion. Above some individual characteristics, we highlighted a contextual effect (air temperature) for the mean heart rate (P = 0.03), the relative cardiac cost (P = 0.01) and, to a lesser extent, a cardiac workload score (P = 0.07). Canopy management by hand in vineyards causes considerable cardiac and thermoregulatory strain. Appropriate instruments should be developed to simultaneously evaluate work intensity, work quality, and productivity at the vineyard level to raise the awareness of both managers and employees about taking preventive measures.

The association between pesticide use and cutaneous melanoma: a systematic review and meta-analysis

BACKGROUND

The incidence of cutaneous melanoma (CM), the deadliest form of skin cancer, has gradually increased in the last decades among populations of European origin. Epidemiological studies suggested that farmers and agricultural workers are at an increased risk of CM because they were exposed to pesticides. However, little is known about the relationship between pesticides and CM.

OBJECTIVES

To investigate the association between exposure to pesticides and CM by systematically reviewing the literature. Secondary aim was to determine the categories of pesticides mainly involved in CM development.

METHODS

A systematic review of the literature was performed up to September 2018 using MEDLINE, Embase and Web of Science. Studies assessing CM risk in licensed pesticide applicators were considered. Strict criteria were established to select independent studies and risk estimates; random effect models, taking into account heterogeneity, were applied. A pooled risk estimate for CM was calculated for the use of each type of pesticide and type of exposure. Between-study and estimate heterogeneity was assessed and publication bias investigated.

RESULTS

A total of nine studies (two case-controls and seven cohorts) comprising 184 389 unique subjects were included. The summary relative risks for the categories 'herbicides - ever exposure', 'insecticides - ever exposure', 'any pesticide - ever exposure' and 'any pesticide - high exposure' resulted 1.85 [95% confidence interval (CI): 1.01, 3.36], 1.57 (95% CI: 0.58, 4.25), 1.31 (95% CI: 0.85, 2.04) and 2.17 (95% CI: 0.45, 10.36), respectively. Herbicides and insecticides had no between-study heterogeneity (I2  = 0%), while a significant heterogeneity (I2  > 50%) was detected for the high exposure to any pesticide. No indication for publication bias was found.

CONCLUSIONS

Individuals exposed to herbicides are at an increased risk of CM. Future properly designed observational studies are required to confirm this finding.

Cancer incidence in the AGRICAN cohort study (2005-2011)

BACKGROUND

Numerous studies have been conducted among farmers, but very few of them have involved large prospective cohorts, and few have included a significant proportion of women and farm workers. Our aim was to compare cancer incidence in the cohort (overall, by sex, and by work on farm, occupational status and pesticide use) within the general population.

METHODS

More than 180,000 participants in the AGRICAN cohort were matched to cancer registries to identify cancer cases diagnosed from enrolment (2005-2007) to 31st December 2011. We calculated standardized incidence ratios (SIRs) and 95% confidence intervals (95%CIs).

RESULTS

Over the period, 11,067 incident cancer cases were identified (7304 men and 3763 women). Overall cancer incidence did not differ between the cohort and the general population. Moreover, SIRs were significantly higher for prostate cancer (SIR=1.07, 95%CI 1.03-1.11) and non-Hodgkin lymphoma (SIR=1.09, 95%CI 1.01-1.18) among men, skin melanoma among women (SIR=1.23, 95%CI 1.05-1.43) and multiple myeloma (men: SIR=1.38, 95%CI 1.18-1.62; women: SIR=1.26, 95%CI 1.02-1.54). In contrast, SIRs were lower for upper aerodigestive tract and respiratory cancers. Increase in risk was greater in male farm workers for prostate and lip cancer, in female farm workers for skin melanoma, and in male farm owners for multiple myeloma. Moreover, incidence of multiple myeloma and skin melanoma was higher among male and female pesticide users respectively.

CONCLUSION

We found a decreased incidence for tobacco-related cancers and an increased incidence of prostate cancers, skin melanoma and multiple myeloma. Specific subgroups had a higher cancer incidence related to occupational status and pesticide use.

Pretreatment with indomethacin results in increased heat stroke severity during recovery in a rodent model of heat stroke

It has been suggested that medications can increase heat stroke (HS) susceptibility/severity. We investigated whether the nonsteroidal anti-inflammatory drug (NSAID) indomethacin (INDO) increases HS severity in a rodent model. Core temperature (T_c) of male, C57BL/6J mice (n = 45) was monitored continuously, and mice were given a dose of INDO [low dose (LO) 1 mg/kg or high dose (HI) 5 mg/kg in flavored treat] or vehicle (flavored treat) before heating. HS animals were heated to 42.4°C and euthanized at three time points for histological, molecular, and metabolic analysis: onset of HS [maximal core temperature (T_c,Max)], 3 h of recovery [minimal core temperature or hypothermia depth (HYPO)], and 24 h of recovery (24 h). Nonheated (control) animals underwent identical treatment in the absence of heat. INDO (LO or HI) had no effect on physiological indicators of performance (e.g., time to T_c,Max, thermal area, or cooling time) during heating or recovery. HI INDO resulted in 45% mortality rate by 24 h (HI INDO + HS group). The gut showed dramatic increases in gross morphological hemorrhage in HI INDO + HS in both survivors and nonsurvivors. HI INDO + HS survivors had significantly lower red blood cell counts and hematocrit suggesting significant hemorrhage. In the liver, HS induced cell death at HYPO and increased inflammation at T_c,Max, HYPO, and 24 h; however, there was additional effect with INDO + HS group. Furthermore, the metabolic profile of the liver was disturbed by heat, but there was no additive effect of INDO + HS. This suggests that there is an increase in morbidity risk with INDO + HS, likely resulting from significant gut injury.NEW & NOTEWORTHY This paper suggests that in a translational mouse model, NSAIDs may be counterindicated in situations that put an individual at risk of heat injury. We show here that a small, single dose of the NSAID indomethacin before heat stroke has a dramatic and highly damaging effect on the gut, which ultimately leads to increased systemic morbidity.

Intervention to reduce heat stress and improve efficiency among sugarcane workers in El Salvador: Phase 1

BACKGROUND

Chronic heat stress and dehydration from strenuous work in hot environments is considered an essential component of the epidemic of chronic kidney disease in Central America.

OBJECTIVE

(1) To assess feasibility of providing an intervention modelled on OSHA's Water.Rest.Shade programme (WRS) during sugarcane cutting and (2) to prevent heat stress and dehydration without decreasing productivity.

METHODS

Midway through the 6-month harvest, the intervention introduced WRS practices. A 60-person cutting group was provided water supplied in individual backpacks, mobile shaded rest areas and scheduled rest periods. Ergonomically improved machetes and efficiency strategies were also implemented. Health data (anthropometric, blood, urine, questionnaires) were collected preharvest, preintervention, mid-intervention and at the end of harvest. A subsample participated in focus group discussions. Daily wet bulb globe temperatures (WBGT) were recorded. The employer provided individual production records.

RESULTS

Over the harvest WBGT was >26°C from 9:00 onwards reaching average maximum of 29.3±1.7°C, around 13:00. Postintervention self-reported water consumption increased 25%. Symptoms associated with heat stress and with dehydration decreased. Individual daily production increased from 5.1 to a high of 7.3 tons/person/day postintervention. This increase was greater than in other cutting groups at the company. Focus groups reported a positive perception of components of the WRS, and the new machete and cutting programmes.

CONCLUSIONS

A WRS intervention is feasible in sugarcane fields, and appears to markedly reduce the impact of the heat stress conditions for the workforce. With proper attention to work practices, production can be maintained with less impact on worker health.

Occupational Exposure to Pesticides With Occupational Sun Exposure Increases the Risk for Cutaneous Melanoma

OBJECTIVE

The objective of the study was to examine the association between occupational exposure to pesticides and cutaneous melanoma, controlling for all possible confounders.

METHODS

A pooled analysis of two case-control studies was conducted in two different geographic areas (Italy and Brazil). Detailed pesticides exposure histories were obtained.

RESULTS

Ever use of any pesticide was associated with a high risk of cutaneous melanoma (odds ratio 2.58; 95% confidence interval 1.18-5.65) in particular exposure to herbicides (glyphosate) and fungicides (mancozeb, maneb), after controlling for confounding factors. When subjects were exposed to both pesticides and occupational sun exposure, the risk increased even more (odds ratio 4.68; 95% confidence interval 1.29-17.0).

CONCLUSIONS

The study suggests an augmented risk of cutaneous melanoma among subjects with exposure to pesticides, in particular among those exposed to occupational sun exposure.

Impaired thermoregulation and beneficial effects of thermoneutrality in the 3×Tg-AD model of Alzheimer's disease

The sharp rise in the incidence of Alzheimer's disease (AD) at an old age coincides with a reduction in energy metabolism and core body temperature. We found that the triple-transgenic mouse model of AD (3×Tg-AD) spontaneously develops a lower basal body temperature and is more vulnerable to a cold environment compared with age-matched controls. This was despite higher nonshivering thermogenic activity, as evidenced by brown adipose tissue norepinephrine content and uncoupling protein 1 expression. A 24-hour exposure to cold (4 °C) aggravated key neuropathologic markers of AD such as: tau phosphorylation, soluble amyloid beta concentrations, and synaptic protein loss in the cortex of 3×Tg-AD mice. Strikingly, raising the body temperature of aged 3×Tg-AD mice via exposure to a thermoneutral environment improved memory function and reduced amyloid and synaptic pathologies within a week. Our results suggest the presence of a vicious cycle between impaired thermoregulation and AD-like neuropathology, and it is proposed that correcting thermoregulatory deficits might be therapeutic in AD.

Temperature modifies the association between particulate air pollution and mortality: A multi-city study in South Korea

Substantial epidemiologic literature has demonstrated the effects of air pollution and temperature on mortality. However, there is inconsistent evidence regarding the temperature modification effect on acute mortality due to air pollution. Herein, we investigated the effects of temperature on the relationship between air pollution and mortality due to non-accidental, cardiovascular, and respiratory death in seven cities in South Korea. We applied stratified time-series models to the data sets in order to examine whether the effects of particulate matter <10 μm (PM10) on mortality were modified by temperature. The effect of PM10 on daily mortality was first quantified within different ranges of temperatures at each location using a time-series model, and then the estimates were pooled through a random-effects meta-analysis using the maximum likelihood method. From all the data sets, 828,787 non-accidental deaths were registered from 2000-2009. The highest overall risk between PM10 and non-accidental or cardiovascular mortality was observed on extremely hot days (daily mean temperature: >99th percentile) in individuals aged <65 years. In those aged ≥65 years, the highest overall risk between PM10 and non-accidental or cardiovascular mortality was observed on very hot days and not on extremely hot days (daily mean temperature: 95-99th percentile). There were strong harmful effects from PM10 on non-accidental mortality with the highest temperature range (>99th percentile) in men, with a very high temperature range (95-99th percentile) in women. Our findings showed that temperature can affect the relationship between the PM10 levels and cause-specific mortality. Moreover, the differences were apparent after considering the age and sex groups.

Assessment of an extended dataset of in vitro human dermal absorption studies on pesticides to determine default values, opportunities for read-across and influence of dilution on absorption

Dermal absorption is a key parameter in non-dietary human safety assessments for agrochemicals. Conservative default values and other criteria in the EFSA guidance have substantially increased generation of product-specific in vitro data and in some cases, in vivo data. Therefore, data from 190 GLP- and OECD guideline-compliant human in vitro dermal absorption studies were published, suggesting EFSA defaults and criteria should be revised (Aggarwal et al., 2014). This follow-up article presents data from an additional 171 studies and also the combined dataset. Collectively, the data provide consistent and compelling evidence for revision of EFSA's guidance. This assessment covers 152 agrochemicals, 19 formulation types and representative ranges of spray concentrations. The analysis used EFSA's worst-case dermal absorption definition (i.e., an entire skin residue, except for surface layers of stratum corneum, is absorbed). It confirmed previously proposed default values of 6% for liquid and 2% for solid concentrates, irrespective of active substance loading, and 30% for all spray dilutions, irrespective of formulation type. For concentrates, absorption from solvent-based formulations provided reliable read-across for other formulation types, as did water-based products for solid concentrates. The combined dataset confirmed that absorption does not increase linearly beyond a 5-fold increase in dilution. Finally, despite using EFSA's worst-case definition for absorption, a rationale for routinely excluding the entire stratum corneum residue, and ideally the entire epidermal residue in in vitro studies, is presented.

Particulate matter modifies the magnitude and time course of the non-linear temperature-mortality association

It remains uncertain whether air pollution modifies the magnitude and time course of the temperature mortality association. We applied a distributed lag non-linear model (DLNM) combined with non-linear interaction terms to assess the modifying effects of particulate matter with an aerodynamic diameter of 10 mm or less (PM(10)) on the association between mean temperature and mortality in Guangzhou, China.We found that both cold and hot effects increased with the quartiles of PM(10). The elderly were more vulnerable to cold and hot effects. Men suffered more from cold-related mortality than women, with the gender difference enlarging with the quartiles of PM(10). We identified statistically significant interaction effects between PM(10) and mean temperature on mortality (except for respiratory mortality). Cold and hot effects basically appeared acutely on highly polluted days, while effects were delayed on lowly polluted days. The findings indicate the importance of reducing PM(10) emission on extremely temperature days.

Effect of the interaction between outdoor air pollution and extreme temperature on daily mortality in Shanghai, China

BACKGROUND

Both outdoor air pollution and extreme temperature have been associated with daily mortality; however, the effect of their interaction is not known.

METHODS

This time-series analysis examined the effect of the interaction between outdoor air pollutants and extreme temperature on daily mortality in Shanghai, China. A generalized additive model (GAM) with penalized splines was used to analyze mortality, air pollution, temperature, and covariate data. The effects of air pollutants were stratified by temperature stratum to examine the interaction effect of air pollutants and extreme temperature.

RESULTS

We found a statistically significant interaction between PM₁₀/O₃ and extreme low temperatures for both total nonaccidental and cause-specific mortality. On days with "normal" temperatures (15th-85th percentile), a 10-µg/m³ increment in PM₁₀ corresponded to a 0.17% (95% CI: 0.03%, 0.32%) increase in total mortality, a 0.23% (0.02%, 0.44%) increase in cardiovascular mortality, and a 0.26% (-0.07%, 0.60%) increase in respiratory mortality. On low-temperature days (<15th percentile), the estimates changed to 0.40% (0.21%, 0.58%) for total mortality, 0.49% (0.13%, 0.86%) for cardiovascular mortality, and 0.24% (-0.33%, 0.82%) for respiratory mortality. The interaction pattern of O₃ with lower temperature was similar. The interaction between PM₁₀/O₃ and lower temperature remained robust when alternative cut-points were used for temperature strata.

CONCLUSIONS

The acute health effects of air pollution might vary by temperature level.

The effect of consequent exposure of stress and dermal application of low doses of chlorpyrifos on the expression of glial fibrillary acidic protein in the hippocampus of adult mice

BACKGROUND

Chlorpyrifos (CPF), a commonly used pesticide worldwide, has been reported to produce neurobehavioural changes. Dermal exposure to CPF is common in industries and agriculture. This study estimates changes in glial fibrillary acidic protein (GFAP) expression in hippocampal regions and correlates with histomorphometry of neurons and serum cholinesterase levels following dermal exposure to low doses of CPF with or without swim stress.

METHODS

Male albino mice were separated into control, stress control and four treatment groups (n = 6). CPF was applied dermally over the tails under occlusive bandage (6 hours/day) at doses of 1/10th (CPF 0.1) and 1/5th dermal LD50 (CPF 0.2) for seven days. Consequent treatment of swim stress followed by CPF was also applied. Serum cholinesterase levels were estimated using spectroflurometric methods. Paraffin sections of the left hippocampal regions were stained with 0.2% thionin followed by the counting of neuronal density. Right hippocampal sections were treated with Dako Envision GFAP antibodies.

RESULTS

CPF application in 1/10th LD50 did not produce significant changes in serum cholinesterase levels and neuronal density, but increased GFAP expression significantly (p < 0.001). Swim stress with CPF 0.1 group did not show increase in astrocytic density compared to CPF 0.1 alone but decreased neuronal density.

CONCLUSIONS

Findings suggest GFAP expression is upregulated with dermal exposure to low dose of CPF. Stress combined with sub-toxic dermal CPF exposure can produce neurotoxicity.