Leukemias and blood dyscrasias following exposure to chlordane and heptachlor

Maternal and Paternal Household Pesticide Exposure During Pregnancy and Risk of Childhood Acute Lymphoblastic Leukemia

OBJECTIVE

The aim of this study was to investigate whether risk estimates for childhood acute lymphoblastic leukemia change when restricting model comparison groups to "nonpesticide exposure" (NPE10) households.

METHODS

Cases ( n = 1810) 15 years or younger were identified through Children's Cancer Group institutions between 1989 and 1993 and age-/sex-matched to controls ( n = 1951). Household pesticide use during pregnancy/month prior was collected via telephone. NPE10 comparison group reporting no parental exposure to 10 pesticide classes was identified.

RESULTS

Adjusted odds ratios increased from 15% to 49% when limiting the comparison to NPE10. Maternal termite insecticide exposure was associated with greatest risk (adjusted odds ratio, 4.21; 95% confidence interval, 2.00-8.88). There was minimal evidence of interaction by child sex or occupational pesticide exposure, and no monotonic dose-response pattern with frequency of use (times per year).

CONCLUSIONS

Elevated risks are consistent with published pooled-/meta-analyses and DNA damage. The consistency and magnitude of these associations warrant product labeling, exposure reduction interventions, or both.

Pre-diagnostic serum concentrations of organochlorines and risk of acute myeloid leukemia: A nested case-control study in the Norwegian Janus Serum Bank Cohort

BACKGROUND

Epidemiologic studies suggest an increased risk of leukemia among individuals occupationally exposed to some organochlorine (OC) compounds. Associations between serum OC pesticide and polychlorinated biphenyl (PCB) levels and risk of acute myeloid leukemia (AML), the most common subtype of acute leukemia in adult populations, have not been evaluated prospectively in the general population.

OBJECTIVE

We evaluated the risk of AML in relation to pre-diagnostic serum levels of OC pesticides and PCBs in a case-control study nested within the Janus Serum Bank Cohort.

METHODS

Janus is a large population-based cohort containing biologic samples collected beginning in the early 1970s from ~318,000 individuals in Norway. Serum levels of 11 OC pesticides or their metabolites and 34 PCB congeners were measured in 56 AML cases and 288 controls. Conditional logistic regression was conducted to evaluate associations between lipid-adjusted serum OC levels and risk of AML.

RESULTS

Higher serum levels of total chlordane/heptachlor metabolites were associated with AML risk (3rd vs. 1st tertile odds ratio (OR) = 2.26, 95% confidence interval (CI) = 0.91-5.63; p_trend = 0.11). Significant exposure-response associations were observed for levels of heptachlor epoxide (3rd vs. 1st tertile OR = 2.85, 95% CI = 1.05-7.73; p_trend = 0.02) and dieldrin (3rd vs. 1st tertile OR = 2.71, 95% CI = 1.07-6.83; p_trend = 0.03). No significant exposure-response associations with AML risk were observed for total DDT or individual isomers and derivatives. Higher serum levels of p,p'-DDT showed a non-significant increase in risk, but the exposure-response became attenuated when co-adjusting for heptachlor epoxide or dieldrin levels. Serum PCB levels were not significantly associated with AML risk.

CONCLUSIONS

Our data suggest that higher serum levels of dieldrin and metabolites derived from chlordane/heptachlor are associated with risk of AML in the general Norwegian population, based on samples collected on average ~17 years before diagnosis. Further research in populations with historically high or recent exposure to DDT is warranted to assess the association with AML risk with body burden of specific DDT isomers and derivatives.

Residential exposure to polychlorinated biphenyls and organochlorine pesticides and risk of childhood leukemia

BACKGROUND

Incidence of childhood leukemia in industrialized countries rose significantly during 1975-2004, and the reasons for the increase are not understood.

OBJECTIVES

We used carpet dust as an exposure indicator to examine the risk of childhood leukemia in relation to residential exposure to persistent organochlorine chemicals: six polychlorinated biphenyl (PCB) congeners and the pesticides alpha- and gamma-chlordane, p,p'-DDT (dichlorodiphenyltrichloroethane), p,p'-DDE (dichlorodiphenyldichloroethylene), methoxychlor, and pentachlorophenol.

METHODS

We conducted a population-based case-control study in 35 counties in northern and central California in 2001-2006. The study included 184 acute lymphocytic leukemia (ALL) cases 0-7 years of age and 212 birth certificate controls matched to cases by birth date, sex, race, and Hispanic ethnicity. We collected carpet dust samples from the room where the child spent the most time before diagnosis (similar date for controls) using a specialized vacuum.

RESULTS

Detection of any PCB congener in the dust conferred a 2-fold increased risk of ALL [odds ratio (OR) = 1.97; 95% confidence interval (CI), 1.22-3.17]. Compared with those in the lowest quartile of total PCBs, the highest quartile was associated with about a 3-fold risk (OR = 2.78; 95% CI, 1.41-5.48), and the positive trend was significant (p = 0.017). Significant positive trends in ALL risk were apparent with increasing concentrations of PCB congeners 118, 138, and 153. We observed no significant positive associations for chlordane, DDT, DDE, methoxychlor, or pentachlorophenol. The associations with PCBs were stronger among non-Hispanic whites than among Hispanics despite similar distributions of PCB levels among controls in each racial/ethnic group.

CONCLUSIONS

Our findings suggest that PCBs, which are considered probable human carcinogens and cause perturbations of the immune system, may represent a previously unrecognized risk factor for childhood leukemia.

Effects of organochlorine pesticides on interleukin secretion from lymphocytes

Organochlorine pesticides have been used worldwide primarily as insecticides. Due to their chemical stability, they often persist in the environment long after their use has ceased. In a previous study, we found that six organochlorine compounds (alpha-chlordane, gamma-chlordane, 4,4'-DDT, heptachlor, oxychlordane, and pentachlorophenol (PCP)), at concentrations of 5 microM, were able to significantly decrease the ability of highly purified human natural killer (NK) cells to lyse tumor cells after exposures, ranging from 1 hour to 6 days. However, if T cells were present with the NK cells (T/NK cells), loss of lytic function was seen only with oxychlordane and PCP. The purpose of the current study is to begin to investigate the mechanism by which T cells may be blocking the negative effects of some organochlorine compounds on NK cell function. Here, we investigated the hypothesis that T cells could produce significant levels of NK-stimulatory interleukin(s) (ILs), and that this may account for the decreased inhibition seen with organochlorine exposures when T cells were present. Secretion of four cytokines that have a demonstrated capacity to influence NK function, and/or are secreted by T cells, was measured (IL-2, IL-4, IL-10, IL-12). We measured both the baseline levels of ILs and the effects of organochlorine compound on IL secretion in T/NK cells. The results showed that baseline levels of the NK-stimulatory IL, IL-12, were 898 +/- 264 pg/mL at 24 hours and IL-10 levels were 564 +/- 337 pg/mL. In contrast, IL-2 levels were 14 +/- 10 pg/mL, and IL-4 levels were 3 +/- 2 pg/mL at 24 hours. The two compounds that retained their capacity to decrease NK lytic function in T/NK cells, oxychlordane (5 microM) and PCP (5 and 10 microM), were able to either decrease the secretion of NK-stimulatory ILs (IL-2, IL-12 and/or IL-10) and/or increase secretion of the NK-inhibitory cytokine, IL-4, at each length of exposure tested.

Occupational exposure to organochlorine insecticides and cancer incidence in the Agricultural Health Study

Organochlorine (OC) insecticides have been regulated as possible human carcinogens primarily on the basis of animal studies. However, the epidemiologic evidence is inconsistent. We investigated the relationship between cancer incidence and OC insecticide use among pesticide applicators enrolled in the Agricultural Health Study, a prospective cohort study of 57,311 licensed applicators in Iowa and North Carolina enrolled between 1993 and 1997. Information on ever use of 7 OC insecticides (aldrin, chlordane, DDT, dieldrin, heptachlor, lindane, toxaphene) was collected from a self-administered questionnaire at enrollment. Lifetime exposure-days to OC insecticides were calculated using additional data from a take-home questionnaire completed by 25,291 participants (44% of total). We found no clear evidence of an association between use of OC insecticides and incident cancers (N = 1,150) ascertained through December, 2002. When we focused on individual insecticides and structurally similar groups (aldrin and dieldrin; chlordane and heptachlor), significantly increased relative risks of some cancers were observed for use of some chemicals (rectal cancer and chlordane, lung cancer and dieldrin, non-Hodgkin lymphoma (NHL) and lindane, melanoma and toxaphene, leukemia and chlordane/heptachlor). Some significant decreased relative risks were also observed (colon cancer and aldrin; overall cancer and heptachlor). In conclusion, we did not observe any clear relationship between cancer risk and the use of OC insecticides. Our chemical-specific findings are based on small numbers and multiple comparisons, and should be interpreted with caution; however, some observed associations (lindane and NHL, chlordane/heptachlor and leukemia) are supported by previous evidence.

Use and storage of domestic pesticides in the UK

Several epidemiological studies, particularly from the United States, have suggested health concerns may arise from the chronic exposure of young children to pesticides in their home environment. Most of these studies are retrospective and the available pesticide exposure information is either subject to the problem of recall or derived from surrogate information. Currently, little is known about the extent of pesticide use in homes and gardens in the UK. This was investigated in this study using a sample of parents from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort in and around Bristol. The level and extent of pesticide use by parents was explored through interviews that took place at the homes of the participants during August to November 2001, followed by an inventory of products stored in the home. From the results, 93% of parents had used at least one pesticide over the preceding year with the highest use being in the garden, second inside the home, followed by treating pets and head lice. Most households reported using one to five different products over the past year, with a mean of 3.5. The frequency of pesticide use showed that a minority of parents are using pesticides in the high frequency range. Over 85 different pesticide products were found to be stored in 76% of homes, with 76 different types of pesticide active ingredients. Insecticides were the most commonly used and stored pesticide.

Environmental exposure to residential pesticides, chemicals, dusts, fumes, and metals, and risk of childhood germ cell tumors

We examined relationships between exposure to residential pesticides, chemicals, dusts, fumes, and metals, and childhood germ cell tumors (GCTs) in the largest case-control study to date on the topic. We recruited 272 children under 15 years old who had GCT diagnosed between January 1, 1993 and December 31, 2001. Controls were selected by random-digit dialing and were frequency matched to cases by sex, age, and geographic area. Telephone interviews and self-administered questionnaires of parents were used to collect exposure information. We used unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). Maternal and paternal exposure from 6 months before pregnancy to during breastfeeding and children's postnatal exposure to residential pesticides were generally unrelated to risk of childhood GCT. Elevated OR were observed for mothers' exposure to hair dyes 1 month before pregnancy for boys (OR = 1.7, 95% CI = 1.0-2.8) and during breastfeeding for boys and girls combined, and for girls (OR = 1.5, 95% CI = 1.0-2.2 and OR = 1.7, 95% CI = 1.1-2.6, respectively). Among boys, OR for paternal exposure to insecticides more often than four times or exposure to indoor insecticides more often than three times were 0.5 (95% CI = 0.2-0.9, trend test p = 0.05) and 0.3 (95% CI = 0.2-0.8, trend test p = 0.02) during the index pregnancy. Overall this study produced no strong evidence linking parental and child residential exposure to pesticides, certain chemicals, dusts, fumes, and metals to increased risk of childhood GCT. Statistically significant associations need to be confirmed in future studies.

Immunomodulation of human natural killer cell cytotoxic function by organochlorine pesticides

Organochlorine pesticides are used worldwide. To our knowledge there have been no studies dealing with the effects of these agents under in vitro conditions on human natural killer (NK) cell cytotoxic function. NK cells play a central role in immune defense against tumor development and viral infections. Thus, any agent that interferes with the ability of NK cells to lyse their targets could increase the risk of tumor incidence and/or viral infections. In this study, we examined the effects of organochlorine pesticides and some of their breakdown products on the ability of human NK cells to lyse tumor cells. A total of 11 compounds were tested. The compounds were tested in both purified NK cells as well as a cell preparation that contained other mononuclear cells (predominantly T cells) and NK lymphocytes (referred to as T/NK cells). Lymphocytes were exposed to the compounds for periods of time ranging from 1 hour to 6 days. Exposure of highly purified NK cells to 5 microM alpha-chlordane, gamma-chlordane, 4,4'-DDT, heptachlor, oxychlordane, or pentachlorophenol (PCP) inhibited their ability to destroy K562 tumor-cells by 88+/-5, 92+/-8, 61+/-13%, 64+/-10%, 69+/-11%, 76+/-12%, respectively, after a 24 h exposure. The loss of cytotoxic function seen with alpha-and gamma-chlordane remained essentially constant out to 6 days, while that seen with 4,4'-DDT, oxychordane and PCP increased with longer exposures (6 d). PCP was the most effective of the compounds tested at decreasing NK function. Of the compounds that caused decreased lytic function when tested in purified NK cells, only PCP and oxychordane decreased the lytic function of the T/NK cell preparation after any exposure. The results provide evidence of relative toxic potential for the 11 compounds and their immunomodulatory effects on other mononuclear cells (such as T-cells, B-cells, and monocytes) as well as NK lymphocyte function.

Modulation of CPP32 activity and induction of apoptosis in Human CEM X 174 lymphocytes by heptachlor, a chlorinated hydrocarbon insecticide

Heptachlor is an organochlorine insecticide used worldwide for the control of pests both agriculturally and domestically. Its lipophilic structure allows it to bioaccumulate and pass through the food chain, exposing those who come in contact with it to its tumor promoting and possible carcinogenic effects. As a mechanism of tumor promotion, we explored the possibility of heptachlor suppressing the apoptotic process in human CEM x 174 lymphocytes. In this article, we describe the effect of heptachlor on the activity of the apoptosis protease CPP32. We show that heptachlor by itself was able to stimulate CPP32 activity at relatively high concentrations. When combined with the chemotherapeutic agent doxorubicin, a known CPP32 activator, a dual effect was observed. Low concentrations of heptachlor (5 microM-10 microM) suppressed doxorubicin-induced CPP32 activity, and high concentrations of heptachlor (80 microM-120 microM) augmented it. We also showed that heptachlor alone at relatively high concentrations induced apoptosis-associated changes in CEM x 174 cells including high molecular weight (HMW) DNA cleavage and chromatin condensation. From these results, it appears that heptachlor has tumor promoting-like effects at lower concentrations, and at higher concentrations induces apoptosis as a mechanism of cytotoxicity.

A cluster of childhood leukemia near a nuclear reactor in northern Germany

Between February 1990 and December 1995, professionals diagnosed six cases of childhood leukemia among residents of the small rural community of Elbmarsch in northern Germany. Five of these cases were diagnosed in only a 16-mo period between February 1990 and May 1991. All cases lived in close proximity (i.e., 500-4,500 m) to Germany's largest capacity nuclear boiling-water reactor. We calculated standardized incidence ratios and exact 95% confidence intervals for a 5-km-radius circular area around the plant. The standardized incidence ratio for the time period 1990-1995 was 460 (95% confidence interval: 210, 1,030). The analysis was restricted further to the years 1990 and 1991, and the standardized incidence ratio increased to 1,180 (95% confidence interval: 490, 2,830). Presently, this cluster of childhood leukemia cases cannot be explained in terms of established and putative risk factors--including radiation from medical sources--for childhood leukemia.

Clinical evaluation of pesticide exposure and poisonings

Pesticide exposures cause disorders varying from straightforward topical irritant reactions, such as those to synthetic pyrethroid insecticides, to complex systemic illness, such as that resulting from cholinesterase inhibition by organophosphate pesticides. The acute illness syndromes associated with pesticides most commonly encountered by clinicians are illustrated here by cases reported to the California Pesticide Illness Surveillance Program. The issues raised include asthma associated with exposure to contaminants in organophosphate insecticides, systemic toxicity of ingested pyrethroids (in children), and illnesses associated with spills or misuse of fumigants.

Organochlorine compounds: Risk of non-Hodgkin's lymphoma and breast cancer?

Organochlorines (i.e., synthetic chlorinated hydrocarbon compounds) are widespread, environmental contaminants that are present throughout the United States. Strong epidemiological evidence has linked occupational exposure to a high incidence of non-Hodgkin's lymphoma. Recently, it has been postulated that exposure to organochlorines increases the risk of developing breast cancer. Human data on this issue remain insufficient, but recent results are very consistent. Observations in human populations of the immunotoxic and hormone-mimicking properties of some organochlorines add biological plausibility to the epidemiologic findings. Limitations in our ability to measure organochlorine exposure still preclude a quantitative risk assessment, relative to these cancer endpoints. Public health action with respect to restriction of ongoing production and use of organochlorines, however, appears warranted for purposes of prevention.

Topical exposure to chlordane reduces the contact hypersensitivity response to oxazolone in BALB/c mice

Previous studies have shown that prenatal exposure to the organochlorine pesticide chlordane significantly decreases the ear swelling response to the contact allergen oxazolone in BALB/c mice. Alterations of macrophage function in the efferent arm of the contact hypersensitivity response have also been reported. In the current study, chlordane was applied topically and the effects of oxazolone-induced contact hypersensitivity were determined. Initially, the reduction in oxazolone-induced ear swelling in topically-exposed female BALB/c mice was compared to 30-day-old BALB/c female mice exposed prenatally to chlordane. Prenatal chlordane exposure induced a 36% reduction in ear swelling compared to a 60% reduction following topical treatment at the challenge phase. Topically-applied chlordane also reduced the oxazolone-induced ear swelling by 40% when applied at sensitization. When applied at both sensitization and challenge, ear swelling was reduced by 71%. In a time-course study, it was determined that chlordane must be applied at the time of sensitization, challenge or both or within 1 h post-challenge to significantly reduce ear swelling. A dose-response study showed that the lowest concentration of chlordane resulting in a significantly reduced ear swelling response was 20 micrograms per ear.

Brain tumor and exposure to pesticides in humans: a review of the epidemiologic data

We examined the relationship between exposure to pesticides and the subsequent development of brain tumors in adults through a critical review of the literature. The results of retrospective case-control studies are conflicting, in part because of biases in the selection of patients and controls, poor definition and ascertainment of the nature and extent of the exposure to pesticides, and a non-uniform approach to the collection of antecedent information. A number of the studies evaluated farmers as a group exposed to pesticides; however, inference about cancer incidence in farmers may reflect not only their possible exposure to pesticides, but also exposure to petrochemical products, exhaust fumes, mineral and organic dusts, and biological exposure to animals and microbes. The great majority of the cohort studies of chemical workers employed in the manufacture of pesticides did not indicate an excess of brain cancer mortality. There have been few cohort studies of pesticide applicators and these revealed elevated but non-significant relative risks for excess mortality due to brain cancer. Existing data are insufficient to conclude that exposure to pesticides is a clear risk factor for brain tumors. Given the conflicting results reported for farmers and pesticide applicators and their contrast to chemical workers, it seems more plausible that exposure to multiple agents and/or other factors, such as genetic predisposition, are most relevant with respect to brain tumor pathogenesis.

Home pesticide use and childhood cancer: a case-control study

The association between childhood cancer and home pesticide use was examined in a case-control study of children under 15 years of age. Parents of 252 children diagnosed with cancer in the Denver area between 1976 and 1983 and of 222 control subjects were interviewed regarding use of home pest extermination, yard treatment, and pest strips. The strongest associations were found for yard treatments and soft tissue sarcomas (odds ratios [ORs] around 4.0) and for use of pest strips and leukemias (ORs between 1.7 and 3.0). These results suggest that use of home pesticides may be associated with some types of childhood cancer.

Correlates of a residential pesticide contamination in a self-selected sample

We evaluated the behavioral, health perception, and physical health correlates of a residential pesticide misapplication on 54 individuals and identified factors differentially related to various levels of distress. Study participants were mainly concerned with health issues and exhibited somatic symptoms. Behavioral actions designed to obtain information regarding exposure levels and to reduce exposure were adopted. We found that factors such as a higher contamination level, involvement in a lawsuit, and belonging to a consumer action group, were strongly related to higher levels of psychological distress and, to a lesser extent, to behaviors, somatic symptoms, and health perceptions.

The effect of organic chlorine compounds and their metabolites present in human milk on newborn mice

The effect of pesticides and their metabolites (DDE, DDT, DDD, alpha, beta and gamma-HCH and PCBs) isolated from human milk on the blood and liver morphology of the mouse were studied. Mouse neonates were fed an extract of the organochlorine compounds in linseed oil for a period of 6 weeks. The lowest dose used in the experiment equalled that which a human infant can receive with its mother's milk, calculated per gram of body weight. Doses 10 and 100 times higher were also used. At the end of the experiment, tissue samples for electron microscopy and blood samples for haemotological examination were taken. Haematological examinations, in mice receiving pesticides, revealed a significant rise in the number of Heinz bodies in erythrocytes and an increased number of lymphocytes. These changes were related to the concentrations of the organic chlorine compounds that the animals were given. Electronmicroscopy demonstrated that organochlorine pesticides at doses equal to that might be received by infants caused proliferation of the smooth endoplasmic reticulum in hepatocytes without any clear damage to other subcellular structures. Doses 10 and 100 times higher resulted in more extensive proliferation of the smooth endoplasmic reticulum, reduction of the rough elements of the endoplasmic reticulum and damage to mitochondria. The latest changes were associated with an increased number of prominent Kupffer cells and the appearance of immigratory cells with traits characteristic of lymphocytes and monocytes.

Corporate crime: why we cannot trust industry-derived safety studies

The control of pesticides, as of all synthetic chemicals, in most industrialized countries relies heavily or even entirely on safety data supplied by the manufacturers. Such a regulatory system can only be effective if the companies conducting and reporting the studies honestly disclose any adverse findings. The record shows, however, that all too often company executives and their scientists knowingly suppress or manipulate information that could affect the licensing and sale of their products. A case in point is the gross manipulation of health and related data on the pesticides heptachlor and chlordane by the U.S. chemical company, Velsicol.

Effect of organochlorine pesticides on the phagocytic activity of bovine milk cells

The effect of a complex of organochlorine compounds on the phagocytic activity of macrophages and neutrophils in milk was assessed in vitro using a mixture of DDT, DDE, DDD, alpha, beta and gamma-HCH and HCB and PCBs in concentrations occurring in milk and in concentrations being multiples of the concentrations in milk. Standard strains 305 and Smith of S. aureus were used for phagocytosis assessment. A suppressing effect of these compounds was observed on the per cent of cells phagocytizing both these strains, with a significant decrease in the number of bacteria of both strains phagocytized by macrophages, and the number of S. aureus strain 305 bacteria phagocytized by neutrophils. The concentrations of the mixture of organochlorine compounds used in the experiment had no significant effect on the number of Smith strain bacteria phagocytized by neutrophils.