Associations between polycyclic aromatic hydrocarbon-related exposures and p53 mutations in breast tumors

A meta-analysis of the carcinogenic effects of particulate matter and polycyclic aromatic hydrocarbons

Urbanization has numerous benefits to human society, but some aspects of urban environments, such as air pollution, can negatively affect human health. Two major air pollutants, particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH), have been classified as carcinogens by the International Agency for Research on Cancer. Here, we answer two questions: (1) What are the carcinogenic effects of PM and PAH exposure? (2) How does carcinogenic risk vary across geographical regions? We performed a comprehensive literature search of peer-reviewed published studies examining the link between air pollution and human cancer rates. Focusing on studies published since 2014 when the last IARC monograph on air pollution was published, we converted the extracted data into relative risks and performed subgroup analyses. Exposure to PM2.5 (per 10 μg/m3) resulted in an 8.5% increase in cancer incidence when all cancer types were combined, and risk for individual cancer types (i.e. lung cancer and adenocarcinoma) was also elevated. PM2.5 was also associated with 2.5% higher mortality due to cancer when all types of cancer were combined, and for individual cancer types (i.e., lung and breast cancer). Exposure to PM2.5 and PM10 posed the greatest risk to lung cancer incidence and mortality in Europe (PM2.5 RR 2.15; PM10 RR 1.26); the risk in Asia and the Americas was also elevated. Exposure to PAH and benzo[a]pyrene significantly increased the pooled risk of cancer incidence (10.8% and 8.0% respectively) at the highest percentile of exposure concentration. Our meta-analyses of studies over the past decade shows that urban air pollution in the form of PM2.5, PM10, and PAH all elevate the incidence and mortality of cancer. We discuss the possible mechanisms of carcinogenesis of PM and PAH. These results support World Health Organization's conclusion that air pollution poses among the greatest health risks to humans living in cities.

Ambient air pollutants and breast cancer stage in Tehran, Iran

This study aimed to examine the impacts of single and multiple air pollutants (AP) on the severity of breast cancer (BC). Data of 1148 diagnosed BC cases (2008-2016) were obtained from the Cancer Research Center and private oncologist offices in Tehran, Iran. Ambient PM10, SO2, NO, NO2, NOX, benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene, and BTEX data were obtained from previously developed land use regression models. Associations between pollutants and stage of BC were assessed by multinomial logistic regression models. An increase of 10 μg/m3 in ethylbenzene, o-xylene, m-xylene, and 10 ppb of NO corresponded to 10.41 (95% CI 1.32-82.41), 4.07 (1.46-11.33), 2.89 (1.08-7.73) and 1.08 (1.00-1.15) increase in the odds of stage I versus non-invasive BC, respectively. Benzene (OR, odds ratio = 1.16, 95% CI 1.01-1.33) and o-xylene (OR = 1.18, 1.02-1.38) were associated with increased odds of incidence of BC stages III & IV versus non-invasive stages. BC stage I and stage III&IV in women living in low SES areas was associated with significantly higher levels of benzene, ethylbenzene, o-xylene, and m-xylene. The highest multiple-air-pollutants quartile was associated with a higher odds of stage I BC (OR = 3.16) in patients under 50 years old. This study provides evidence that exposure to AP is associated with increased BC stage at diagnosis, especially under premenopause age.

Metabolic capacity to alter polycyclic aromatic hydrocarbons and its microbe-mediated remediation

The elimination of contaminants caused by anthropogenic activities and rapid industrialization can be accomplished using the widely used technology of bioremediation. Recent years have seen significant advancement in our understanding of the bioremediation of coupled polycyclic aromatic hydrocarbon contamination caused by microbial communities including bacteria, algae, fungi, yeast, etc. One of the newest techniques is microbial-based bioremediation because of its greater productivity, high efficiency, and non-toxic approach. Microbes are appealing candidates for bioremediation because they have amazing metabolic capacity to alter most types of organic material and can endure harsh environmental conditions. Microbes have been characterized as extremophiles that can survive in a variety of environmental circumstances, making them the treasure troves for environmental cleanup and the recovery of contaminated soil. In this study, the mechanisms underlying the bioremediation process as well as the current situation of microbial bioremediation of polycyclic aromatic hydrocarbon are briefly described.

Ambient Fine Particulate Matter and Cancer: Current Evidence and Future Perspectives

The high incidence of cancer has placed an enormous health and economic burden on countries around the world. In addition to evidence of epidemiological studies, conclusive evidence from animal experiments and mechanistic studies have also shown that morbidity and mortality of some cancers can be attributed to ambient fine particulate matter (PM_2.5) exposure, especially in lung cancer. However, the underlying carcinogenetic mechanisms of PM_2.5 remain unclear. Furthermore, in terms of risks of other types of cancer, both epidemiological and mechanistic evidence are more limited and scattered, and the results are also inconsistent. In order to sort out the carcinogenic effect of PM_2.5, this paper reviews the association of cancers with PM_2.5 based on epidemiological and biological evidence including genetic, epigenetic, and molecular mechanisms. The limitations of existing researches and the prospects for the future are also well clarified in this paper to provide insights for future studies.

The impact of endocrine disrupting compounds and carcinogens in wastewater: Implications for breast cancer

The incidence of breast cancer is often associated with geographic variation which indicates that a person's surrounding environment can be an important etiological factor in cancer development. Environmental risk factors can include exposure to sewage- or wastewater, which consist of a complex mixture of pathogens, mutagens and carcinogens. Wastewater contains primarily carbonaceous, nitrogenous and phosphorus compounds, however it can also contain trace amounts of chemical pollutants including toxic metal cations, hydrocarbons and pesticides. More importantly, the contamination of drinking water by wastewater is a potential source of exposure to mammary carcinogens and endocrine disrupting compounds. Organic solvents and other pollutants often found in wastewater have been detected in various tissues, including breast and adipose tissues. Furthermore, these pollutants such as phenolic compounds in some detergents and plastics, as well as parabens and pesticides can mimic estrogen. High estrogen levels are a well-established risk factor for estrogen-receptor (ER) positive breast cancer. Therefore, exposure to wastewater is a risk factor for the initiation, progression and metastasis of breast cancer. Carcinogens present in wastewater can promote tumourigenesis through various mechanisms, including the formation of DNA adducts, gene mutations and oxidative stress. Lastly, the presence of endocrine disrupting compounds in wastewater can have negative implications for ER-positive breast cancers, where these molecules can activate ERα to promote cell proliferation, survival and metastasis. As such, strategies should be implemented to limit exposure, such as providing funding into treatment technologies and implementation of regulations that limit the production and use of these potentially harmful chemicals.

Bibliometric analysis of global research on polycyclic aromatic hydrocarbons and health risk between 2002 and 2021

During the last 20 years, the association between polycyclic aromatic hydrocarbons (PAHs) and health risk has become one of the hotspots in the fields of public health and the environment. A bibliometric study of 1392 research articles retrieved from the Web of Science Core Collection (WoSCC) published between 2002 and 2021 was performed to give an in-depth statistical evaluation of research progress and future trends on PAHs and health risk (PHR). According to the findings, the annual output of significant scientific papers increased exponentially. China ranked first among the 86 nations in terms of the number of publications (NP), followed by the USA and India. Logistic regression analysis showed that there was a positive relationship between the second tertile of 180-day usage count (AOR = 1.62; 95% CI: 1.16-2.26) and increased odds of open access publishing after adjustment for the confounders, indicating that open access papers on PHR were more preferred over the preceding 6 months than non-open access articles. The most popular terms were "PAHs," "risk assessment," and "source identification." According to the bibliometric study, the research hotspots that require more exploration include identifying PAH sources in media such as soil, water, dust, and food and evaluating their linkages to health hazards using appropriate risk models. Understanding the environmental behavior, bioavailability, and health concerns of PAHs and their derivatives in various media is critical for environmental and public health protection. This paper provides an overview of current research status and future perspectives for PHR research.

Air Quality and Cancer Prevalence Trends across the Sub-Saharan African Regions during 2005-2020

Poor air quality and environmental pollution remain some of the main etiological factors leading to cancers and cancer-related deaths worldwide. As a result of human activities, deleterious airborne chemicals can be dispersed not only in the environment but also released in occupational environments and industrial areas. Air pollutants and cancer links are now established through various oxidative stress-related mechanisms and related DNA damages. Generally, ambient and indoor air pollutants have been understudied in sub-Saharan Africa (SSA) compared to other regions in the world. Our study not only highlights the deleterious effects of air pollutants in these developing countries, but it has strived to examine the trends and correlations between cancers and some air pollutants-carbon dioxide, other greenhouse gases, PM_2.5, and human development index-in some SSA countries, where recent cancer burdens were reported as high. Our results showed strikingly higher yearly trends of cancers and above-mentioned air pollutant levels in some sub-Saharan countries during 2005-2020. Relative risks (RR) of these air pollutants-related cancer case rates were, however, below, or slightly above 1.0, or not statistically significant possibly due to other responsible and confounding factors which were not considered in our analyses due to data unavailability. We recommend new approaches to monitoring, minimizing, and creating awareness of the trends of hazardous air pollutants in sub-Saharan Africa, which will help ameliorate cancer prevalence and support the reduction in air pollution levels within regulatory limits, thereby relieving the cumulative burdens of cancers. Utilization of the findings from the study will support large-scale public health and health policy efforts on cancer management through environmental stewardship in SSA countries having the poorest outcome and the shortest survival rates from cancers.

Epidemiologic evidence of exposure to polycyclic aromatic hydrocarbons and breast cancer: A systematic review and meta-analysis

Breast cancer (BC) is the most frequently diagnosed cancer in women. However, only 58% of cases have been associated with known risk factors (reproductive, hormonal, lifestyles, and genetic), and the rest to unknown causes. Nevertheless, growing evidence suggests that exposure to environmental contaminants is an important risk factor for BC. Polycyclic aromatic hydrocarbons (PAHs) are formed during organic matter combustion, including smoking, grilled meat, and fuels, and are important carcinogenic constituents of environmental pollution. We examined the information generated by epidemiological studies evaluating the association between BC and PAHs exposure from multiple sources. Our work was conducted according to Conducting Systematic Reviews and Meta-Analyses of Observational Studies of Etiology (COSMOS-E) guidelines. We searched PubMed, Web of Science, and Scopus from January 2000 to December 2019. A total of 124 records were identified, and only 23 articles met all inclusion criteria. Occupational and/or environmental exposure to PAHs was significantly associated with BC, irrespective of exposure being assessed by direct or indirect methods. CYP1A1 and CYP1B1 adverse polymorphisms, familial BC history and smoking status, significantly strengthened the association between PAHs exposure and BC, whereas high fruit and vegetable intake had antagonistic associations. The positive relationships obtained in the studies here reviewed indicated that PAHs exposure is a risk factor for BC. Research needs include the improvement of exposure assessment, particularly identification of specific PAHs, reconstruction of time-varying and distant past exposures and further studies on the interaction between known BC factors and modifiable diet and life-style factors allowing BC prevention and control.

Correlation of Occupational Exposure to Carcinogenic Polycyclic Aromatic Hydrocarbons (cPAHs) and Blood Levels of p53 and p21 Protiens

Carcinogenic polycyclic aromatic hydrocarbons (cPAHs) are considered the most serious cancer risk. This study was conducted to assess the effect of acute exposure to cPAHs on cancer biomarker proteins p53 and p21 in occupational workers during the hajj season in Makkah. One hundred five participants were recruited, including occupational workers and apparently healthy individuals; air samples were collected using personal sample monitors to identify the subjects’ exposure to cPAHs. Quantitative analyses of benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), dibenzo(a,h)fluronathene (DBA), indeno(1,2,3-c,d)pyrene (IND) and chyresene (CRY) were carried out using the GC/Mass technique. Serum p53 and p21 proteins were analyzed using ELISA. The ambient air samples collected by the occupationally exposed group were more highly polluted by cPAHs, (90.25 ± 14.1) ng/m³, than those of the unexposed control groups, (30.12 ± 5.56) ng/m³. The concentration of distributive cPAHs was markedly more elevated in the air samples of the exposed group than in those taken from the non-exposed group. The study results demonstrated significant links between short-term exposure to cPAHs and serum p53 and p21 levels. Serum p53 and p21 proteins potentially influence biomarkers when exposed to ambient air cPAHs.

Association between long-term ambient air pollution exposure and the risk of breast cancer: a systematic review and meta-analysis

Breast cancer is a complex and multifactorial disease which stems significantly from both environmental and genetic factors. A growing number of epidemiological studies have suggested that ambient air pollution (AAP) exposure may play an important role in breast cancer development. However, no consistency has been reached concerning whether high levels of air pollutant exposure were related to increased breast cancer risk among the current evidence. To further clarify such association of long-term AAP exposure with risk of breast cancer, a systematic review and meta-analysis of available evidence was performed. An extensive literature search in 3 academic databases was conducted before March 10, 2020. The risk of bias (RoB) for each individual study was evaluated with a domain-based assessment tool, developed by the National Toxicology Program/Office of Health Assessment and Translation (NTP/OHAT). Meta-estimates for air pollutant-breast cancer combinations were calculated for a standardized increment in exposure by random-effect models. The confidence level in the body of evidence and the certainty of evidence was also assessed for each air pollutant-breast cancer combination. The initial search identified 5446 studies, and 18 of them were eligible. The pooled analysis found an increased risk of breast cancer was associated with an increase in each 10 μg/m³ in nitrogen dioxide (NO₂) exposure (hazard ratio (HR) = 1.02, 95% confidence interval (CI) = 1.01, 1.04), while particulate matter with aerodynamic diameters ≤ 2.5 μm and 10 μm (PM_2.5, PM₁₀) revealed no statistically significant associations with breast cancer risk. Our evaluation on the certainty of evidence indicates that there was a "moderate level of evidence" in the body of evidence for an association of NO₂ exposure with an increased breast cancer risk and an "inadequate level of evidence" in the body of evidence for an association of PM_2.5 and PM₁₀ exposure with an increased breast cancer risk. Our study suggests long-term exposure to NO₂ is related to an increased risk of breast cancer. However, in consideration of the limitations, further studies, especially performed in developing countries, with improvements in exposure assessment, outcome ascertainment, and confounder adjustment, are needed to draw a definite evidence of a causal relationship.

Genetic Variations in Cytochrome P450 1A1 and 1B1 Genes in a Cohort of Patients from Iraq Diagnosed with Breast Cancer

Breast cancer is the most prevalent malignant neoplasm in females. Genetic variations in the xenobiotic metabolising cytochrome enzymes; Family 1 Subfamily A Member 1 (CYP1A1) and Family 1 Subfamily B Member 1 (CYP1B1) might play a role in the individual susceptibility to breast cancer and its prognosis. The goal of this study is to estimate the incidence of single nucleotide polymorphisms (SNPs) in CYP1A1 (rs1048943, Ile462VaI, and rs4646903/MSP1) and in CYP1B1 (rs1056836, Leu432Val) genes in patients with breast cancer. This case-control study included 180 female patients with breast cancer and 180 healthy control subjects from Kirkuk/Iraq. Genomic DNA was extracted from venous blood samples and tested for SNPs by the direct DNA sequencing technique. A statistical analysis was done to identify if there is any association between SNPs and the increasing odd of breast cancer and its stage, grade and molecular subtype at diagnosis. The common (reference) genotype of CYP1A1 gene rs1048943 is AA. The AG and GG variant genotypes were significantly more common in the breast cancer patients and conferred an increased odd of breast cancer and its later stages (stages III and IV) and poor differentiation (P < .01) but not with the molecular subtypes. The common genotype of CYP1A1 rs4646903 is TT. The variant genotypes TC and CC are not associated either with increased risk of breast cancer (P > .05) or with its stage, grade or molecular subtypes (P > .05). The GG genotype of CYP1B1 rs1056836 was the common genotype. The CG and CC variant genotypes were not associated with the increased risks of breast cancer (P > .05) or its stage, grade or molecular subtypes (P > .05). In conclusion, variants genotypes of CYP1A1 rs1048943 might play a role in breast cancer pathogenesis and prognosis and can have a place in cancer screening and tailored medicine in the future in the Iraqi population. Future larger scale studies including other genes might help to better understand the role of the SNP in breast risk and its prognosis.

DNA damage in cancer development: special implications in viral oncogenesis

DNA lesions arise from a combination of physiological/metabolic sources and exogenous environmental influences. When left unrepaired, these alterations accumulate in the cells and can give rise to mutations that change the function of important proteins (i.e. tumor suppressors, oncoproteins), or cause chromosomal rearrangements (i.e. gene fusions) that also result in the deregulation of key cellular molecules. Progressive acquisition of such genetic changes promotes uncontrolled cell proliferation and evasion of cell death, and hence plays a key role in carcinogenesis. Another less-studied consequence of DNA damage accumulating in the host genome is the integration of oncogenic DNA viruses such as Human papillomavirus, Merkel cell polyomavirus, and Hepatitis B virus. This critical step of viral-induced carcinogenesis is thought to be particularly facilitated by DNA breaks in both viral and host genomes. Therefore, the impact of DNA damage on carcinogenesis is magnified in the case of such oncoviruses via the additional effect of increasing integration frequency. In this review, we briefly present the various endogenous and exogenous factors that cause different types of DNA damage. Next, we discuss the contribution of these lesions in cancer development. Finally, we examine the amplified effect of DNA damage in viral-induced oncogenesis and summarize the limited data existing in the literature related to DNA damage-induced viral integration. To conclude, additional research is needed to assess the DNA damage pathways involved in the transition from viral infection to cancer. Discovering that a certain DNA damaging agent increases the likelihood of viral integration will enable the development of prophylactic and therapeutic strategies designed specifically to prevent such integration, with an ultimate goal of reducing or eliminating these viral-induced malignancies.

Deep frying cooking oils promote the high risk of metastases in the breast-A critical review

Deep-frying is the most common food preparation method, manifestations of color, taste, flavor, and fried consistency. The beneficial role of vegetable oils become deteriorate when repeatedly treated with higher temperature and air. Repeatedly heated cooking oils (RCO) produce various byproducts, containing polycyclic aromatic hydrocarbons (PAHs) and aldehydes, well-known to be a carcinogenic, mutagenic, and tumorigenic properties. RCO is nowadays one of the often consumed media for cooking and frying, which intake can cause various unhealthy adverse effects including various cancer in the multiple organs. Hence, the present comprehensive study targets to provide the intake of RCO elevate the risks of human breast cancer. The data on RCO and its impacts were obtained via various electronic findings and library databases. Notable studies have confirmed that the effects of RCO have been attributed to their unfavorable effects, and underlying molecular mechanisms can also strongly promoting tumorigenic effects in the mammary organ.

Concentration levels and carcinogenic and mutagenic risks of PM2.5-bound polycyclic aromatic hydrocarbons in an urban-industrial area in South Africa

Concerns over the health effects of exposure to particulate matter of aerodynamic diameter of less than 2.5 μm (PM_2.5) led the South African Government to establish the national standard for PM_2.5 in the year 2012. However, there is currently no exposure limit for polycyclic aromatic hydrocarbons (PAHs) and PM_2.5-bound PAHs. The understanding of the concentration levels and potential health risks of exposure to PM_2.5-bound PAHs is important in ensuring a suitable risk assessment and risk management plans. This study, therefore, determined the concentration levels and carcinogenic and mutagenic health risks of PM_2.5-bound PAHs. A hundred and forty-four PM_2.5 samples were collected over 4 months during the winter and summer seasons of 2016 in an industrial area. The concentrations of 16 PAHs were analysed by gas chromatography-mass spectrometry, and their carcinogenic and mutagenic risks were determined using the Human Health Risk Assessment model. The mean winter (38.20 ± 8.4 μg/m³) and summer (22.3 ± 4.1 μg/m³) concentrations of PM_2.5 levels were lower than the stipulated 40 μg/m³ daily limit. The daily inhalation and ingestion exposure to PAHs for all age groups were higher than the daily exposure through the dermal contact. Children and adults are more likely to inhale and ingest PAHs in PM_2.5 than infants. The excess cancer risk and excess mutagenic risk values were below the priority risk level (10^-4). There is a potential risk of 1-8 per million persons developing cancer from exposure to benzo[a]anthracene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, and dibenz[a,h]anthracene over a lifetime of 70 years.

Gene expression profiles for low-dose exposure to diethyl phthalate in rodents and humans: a translational study with implications for breast carcinogenesis

Phthalates are commonly included as ingredients in personal care products such as cosmetics, shampoos and perfumes. Diethyl phthalate (DEP) has been found to be anti-androgenic and linked with adverse reproductive effects on males, but effects on females are poorly understood. We designed an integrative and translational study to experimentally examine the effects of DEP exposure at a human-equivalent dose on the mammary transcriptome in rats and to subsequently examine the DEP gene signature in breast tissues (both pre-malignant and tumor) from a population study. In Sprague-Dawley rats treated orally with DEP from birth to adulthood, we identified a signature panel of 107 genes predominantly down-regulated by DEP exposure. Univariate analysis of this 107 DEP gene signature in pre-malignant breast tissues revealed that six genes (P4HA1, MPZL3, TMC4, PLEKHA6, CA8, AREG) were inversely associated with monoethyl phthalate (MEP; the urinary metabolite of DEP) concentration (p < 0.05) among postmenopausal women; all six genes loaded on to one of seven factors identified by factor analysis. Transcription factor enrichment analysis revealed that genes in this factor were enriched for androgen receptor binding sites. These six genes were also significantly down-regulated in pre-malignant adjacent tissues compared to the corresponding tumor tissues in pair-wise analyses (p < 0.05). Results from our translational study indicate that low level exposure to diethyl phthalate results in measurable genomic changes in breast tissue with implications in breast carcinogenesis.

Impact of air pollution on breast cancer incidence and mortality: a nationwide analysis in South Korea

Breast cancer is one of the major female health problems worldwide. Although there is growing evidence indicating that air pollution increases the risk of breast cancer, there is still inconsistency among previous studies. Unlike the previous studies those had case-control or cohort study designs, we performed a nationwide, whole-population census study. In all 252 administrative districts in South Korea, the associations between ambient NO2 and particulate matter 10 (PM10) concentration, and age-adjusted breast cancer mortality rate in females (from 2005 to 2016, Nmortality = 23,565), and incidence rate (from 2004 to 2013, Nincidence = 133,373) were investigated via multivariable beta regression. Population density, altitude, rate of higher education, smoking rate, obesity rate, parity, unemployment rate, breastfeeding rate, oral contraceptive usage rate, and Gross Regional Domestic Product per capita were considered as potential confounders. Ambient air pollutant concentrations were positively and significantly associated with the breast cancer incidence rate: per 100 ppb CO increase, Odds Ratio OR = 1.08 (95% Confidence Interval CI = 1.06-1.10), per 10 ppb NO2, OR = 1.14 (95% CI = 1.12-1.16), per 1 ppb SO2, OR = 1.04 (95% CI = 1.02-1.05), per 10 µg/m3 PM10, OR = 1.13 (95% CI = 1.09-1.17). However, no significant association between the air pollutants and the breast cancer mortality rate was observed except for PM10: per 10 µg/m3 PM10, OR = 1.05 (95% CI = 1.01-1.09).

The relationship between exposure to particulate matter and breast cancer incidence and mortality: A meta-analysis

BACKGROUND

Particulate matter (PM) acts as an environment pollutant and thus plays a vital role in the development of human lung cancer. Whether PM is a risk factor for breast cancer (BC) morbidity and mortality, however, is not clear. Recently, several studies have reported inconsistent results for the association between PM and BC risk. This meta-analysis examines the indefinite relationship between exposure to PM and BC morbidity and mortality.

METHODS

Based on a search of Pubmed, Embase, Web of Science and Cochrane Library, the hazard ratio (HR) and 95% confidence interval (CI) were extracted and analyzed by Review Manager 5.3 and Stata14.0 to estimate the association between PM and BC morbidity and mortality. The heterogeneity for the included studies was evaluated using a Chi-square test and the I statistic. Forest plot was used to illustrate the pooled HR and mean difference. A Funnel plot, Begg test, and Egger test were performed to explore the publication bias between the included studies.All analyses were based on previous published studies, thus, no ethical approval and patient consent are required.

RESULTS

A total of 14 of 284 publications with 1,004,128 BC cases were gathered. The analysis showed each 10 μg/m of PM2.5 (diameter ≤2.5 μm) was associated with 1.17 (95% CI: 1.05-1.30, P = .004) fold risk BC mortality, and each 10 μg/m of PM10 (diameter ≤10 μm) was associated with 1.11 (95% CI: 1.02-1.21, P = .021) fold risk BC mortality. However, neither PM10 nor PM2.5 was found to be significantly associated with BC morbidity. Publication bias was detected in studies on PM2.5 and BC mortality.

CONCLUSIONS

Our study suggests that PM exposure may raise the mortality but not the morbidity of BC. Still, further studies may be necessary to confirm this finding.

DNA Damage and Associated DNA Repair Defects in Disease and Premature Aging

Genetic information is constantly being attacked by intrinsic and extrinsic damaging agents, such as reactive oxygen species, atmospheric radiation, environmental chemicals, and chemotherapeutics. If DNA modifications persist, they can adversely affect the polymerization of DNA or RNA, leading to replication fork collapse or transcription arrest, or can serve as mutagenic templates during nucleic acid synthesis reactions. To combat the deleterious consequences of DNA damage, organisms have developed complex repair networks that remove chemical modifications or aberrant base arrangements and restore the genome to its original state. Not surprisingly, inherited or sporadic defects in DNA repair mechanisms can give rise to cellular outcomes that underlie disease and aging, such as transformation, apoptosis, and senescence. In the review here, we discuss several genetic disorders linked to DNA repair defects, attempting to draw correlations between the nature of the accumulating DNA damage and the pathological endpoints, namely cancer, neurological disease, and premature aging.

Exposure to ambient air pollution and the incidence of lung cancer and breast cancer in the Ontario Population Health and Environment Cohort

Lung and female breast cancers are highly prevalent worldwide. Although the association between exposure to ambient fine particulate matter (PM_2.5 ) and lung cancer has been recognized, there is less evidence for associations with other common air pollutants such as nitrogen dioxide (NO₂ ) and ozone (O₃ ). Even less is known about potential associations between these pollutants and breast cancer. We conducted a population-based cohort study to investigate the associations of chronic exposure to PM_2.5 , NO₂ , O₃ and redox-weighted average of NO₂ and O₃ (O_x ) with incident lung and breast cancer, using the Ontario Population Health and Environment Cohort (ONPHEC), which includes all long-term residents aged 35-85 years who lived in Ontario, Canada, 2001-2015. Incident lung and breast cancers were ascertained using the Ontario Cancer Registry. Annual estimates of exposures were assigned to the residential postal codes of subjects for each year during follow-up. We used Cox proportional-hazards models adjusting for personal- and neighborhood-level covariates. Our cohorts for lung and breast cancer analyses included ~4.9 million individuals and ~2.5 million women, respectively. During follow-up, 100,146 incident cases of lung cancer and 91,146 incident cases of breast cancer were diagnosed. The fully adjusted analyses showed positive associations of lung cancer incidence with PM_2.5 (hazard ratio [HR] = 1.02 [95% CI: 1.01-1.05] per 5.3 μg/m³ ) and NO₂ (HR = 1.05 [95% CI: 1.03-1.07] per 14 ppb). No associations with lung cancer were observed for O₃ or O_x . Relationships between PM_2.5 and NO₂ with lung cancer exhibited a sublinear shape. We did not find compelling evidence linking air pollution to breast cancer.

Toxicological evaluation of airborne particulate matter. Are cell culture technologies ready to replace animal testing?

Exposure to atmospheric particulate matter (PM) can affect human health, causing asthma, atherosclerosis, renal disease and cancer. In the last few years, outdoor air pollution has increased globally, leading to a public health emergency. Epidemiological studies have reported a correlation between the development of severe respiratory and systemic diseases and exposure to PM. To evaluate the toxic effect of PM of different origins, conventional experimental toxicological investigations have been conducted in animals; however, animal experimentation poses major ethical issues and usually differs from human conditions. As an alternative, human cell cultures are increasingly being used to investigate cellular and molecular mechanisms of PM toxicity. Although 2D cell cultures have been proven helpful, they are far from being a valid alternative to animal tests. Recently, 3D cell culture and organ-on-chip technology have provided systems that are more complex and that can be more informative for toxicity studies. In this review, the results of the 2D systems that are most frequently used for PM toxicity evaluations are summarized with a special focus on their limitations. We also examined to which extent 3D cell culture and particularly the organ-on-chip technology may overcome these limitations and represent effective tools to improve airborne PM toxicity evaluations.

The Photodynamic Properties and the Genotoxicity of Heat-Treated Silicalite-1 Films

We investigated the use of a supported silicalite-1 film (SF) as a promising coating for metallic materials used in the fabrication of prostheses. The role of carbonaceous residua present on high-temperature calcined-SF in generating singlet oxygen for future use as a sterilization method has also been addressed, and the potential genotoxicity of these residua in osteoblast-like cells has been investigated. Calcination of as-synthesized SF induced the appearance of a rather complicated mixture of aliphatic and aromatic species on its outer surface. A series of variously volatile polycyclic aromatic hydrocarbons (PAH), including naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene, were identified in micromole concentrations. Irradiation of these PAHs on calcined-SF immersed in air-saturated chloroform led to the formation of very low concentrations of singlet oxygen. However, an increased level of DNA damage was observed on calcined-SF by immunofluorescence staining of phosphorylated histone H2AX analyzed by flow cytometry.

Modular Design of Fluorescent Dibenzo- and Naphtho-Fluoranthenes: Structural Rearrangements and Electronic Properties

A library of 12 dibenzo- and naphtho-fluoranthene polycyclic aromatic hydrocarbons (PAHs) with MW = 302 (C₂₄H₁₄) was synthesized via a Pd-catalyzed fluoranthene ring-closing reaction. By understanding the various modes by which the palladium migrates during the transformation, structural rearrangements were bypassed, obtaining pure PAHs in high yields. Spectroscopic and electrochemical characterization demonstrated the profound diversity in the electronic structures between isomers. Highlighting the significant differences in emission of visible light, this library of PAHs will enable their standardization for toxicological assessment and potential use as optoelectronic materials.

Environmental chemicals and breast cancer: An updated review of epidemiological literature informed by biological mechanisms

BACKGROUND

Many common environmental chemicals are mammary gland carcinogens in animal studies, activate relevant hormonal pathways, or enhance mammary gland susceptibility to carcinogenesis. Breast cancer's long latency and multifactorial etiology make evaluation of these chemicals in humans challenging.

OBJECTIVE

For chemicals previously identified as mammary gland toxicants, we evaluated epidemiologic studies published since our 2007 review. We assessed whether study designs captured relevant exposures and disease features suggested by toxicological and biological evidence of genotoxicity, endocrine disruption, tumor promotion, or disruption of mammary gland development.

METHODS

We systematically searched the PubMed database for articles with breast cancer outcomes published in 2006-2016 using terms for 134 environmental chemicals, sources, or biomarkers of exposure. We critically reviewed the articles.

RESULTS

We identified 158 articles. Consistent with experimental evidence, a few key studies suggested higher risk for exposures during breast development to dichlorodiphenyltrichloroethane (DDT), dioxins, perfluorooctane-sulfonamide (PFOSA), and air pollution (risk estimates ranged from 2.14 to 5.0), and for occupational exposure to solvents and other mammary carcinogens, such as gasoline components (risk estimates ranged from 1.42 to 3.31). Notably, one 50-year cohort study captured exposure to DDT during several critical windows for breast development (in utero, adolescence, pregnancy) and when this chemical was still in use. Most other studies did not assess exposure during a biologically relevant window or specify the timing of exposure. Few studies considered genetic variation, but the Long Island Breast Cancer Study Project reported higher breast cancer risk for polycyclic aromatic hydrocarbons (PAHs) in women with certain genetic variations, especially in DNA repair genes.

CONCLUSIONS

New studies that targeted toxicologically relevant chemicals and captured biological hypotheses about genetic variants or windows of breast susceptibility added to evidence of links between environmental chemicals and breast cancer. However, many biologically relevant chemicals, including current-use consumer product chemicals, have not been adequately studied in humans. Studies are challenged to reconstruct exposures that occurred decades before diagnosis or access biological samples stored that long. Other problems include measuring rapidly metabolized chemicals and evaluating exposure to mixtures.

Development of an in Vitro-Based Risk Assessment Framework for Predicting Ambient Particulate Matter-Bound Polycyclic Aromatic Hydrocarbon-Activated Toxicity Pathways

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed throughout the atmosphere as mixtures attached to ambient particulate matter (PM). PAHs usually elicit similar toxicological pathways but do so with varying levels of efficacy. In this study, we utilized high-throughput screening (HTS) in vitro data of PAHs to predict health risks associated with coarse and fine PM. PM samples with 22 PAH compounds obtained from residential areas close to industrial parks in central Taiwan were analyzed. On the basis of the PM-bound PAH concentrations and their activities reported in HTS assays, we developed a probabilistic model for estimating cumulative exposure of humans to PAHs. Activity-to-exposure ratio (AER) values were calculated to compare relative risks of activating the aryl hydrocarbon receptor (AhR), nuclear factor erythroid 2-related factor 2 (Nrf2), and tumor suppressor gene (p53) when children or adults were exposed to fine or coarse PM in different seasons. On the basis of AER values, the risk of fine PM exposure was relatively higher than the risk of exposure to coarse PM in pathway activation. Children as a susceptible population had a risk of the activating AhR pathway greater than that of adults. Particularly higher risks were observed in winter than in summer. Among three pathways, AhR was the most sensitive one activated by exposure to PAHs. In addition, the activation of the AhR, Nrf2, and p53 pathways was compared by in vitro reporter assays with and without the pre-extraction of PAHs from PM. Our proposed novel approach accounts for mixture toxicities in characterizing in vitro pathway-based risks via inhalation exposure to ambient PAHs.

Cell death pathways of particulate matter toxicity

Humans are exposed to various complex mixtures of particulate matter (PM) from different sources. Long-term exposure to high levels of these particulates has been linked to a diverse range of respiratory and cardiovascular diseases that have resulted in hospital admission. The evaluation of the effects of PM exposure on the mechanisms related to cell death has been a challenge for many researchers. Therefore, in this review, we have discussed the effects of airborne PM exposure on mechanisms related to cell death. For this purpose, we have compiled literature data on PM sources, the effects of exposure, and the assays and models used for evaluation, in order to establish comparisons between various studies. The analysis of this collected data suggested divergent responses to PM exposure that resulted in different cell death types (apoptosis, autophagy, and necrosis). In addition, PM induced oxidative stress within cells, which appeared to be an important factor in the determination of cell fate. When the levels of reactive oxygen species were overpowering, the cellular fate was directed toward cell death. This may be the underlying mechanism of the development or exacerbation of respiratory diseases, such as emphysema and chronic obstructive pulmonary diseases. In addition, PM was shown to cause DNA damage and the resulting mutations increased the risk of cancer. Furthermore, several conditions should be considered in the assessment of cell death in PM-exposed models, including the cell culture line, PM composition, and the interaction of the different cells types in in vivo models.

Long-Term Exposure to Ambient Air Pollution and Incidence of Postmenopausal Breast Cancer in 15 European Cohorts within the ESCAPE Project

BACKGROUND

Epidemiological evidence on the association between ambient air pollution and breast cancer risk is inconsistent.

OBJECTIVE

We examined the association between long-term exposure to ambient air pollution and incidence of postmenopausal breast cancer in European women.

METHODS

In 15 cohorts from nine European countries, individual estimates of air pollution levels at the residence were estimated by standardized land-use regression models developed within the European Study of Cohorts for Air Pollution Effects (ESCAPE) and Transport related Air Pollution and Health impacts – Integrated Methodologies for Assessing Particulate Matter (TRANSPHORM) projects: particulate matter (PM) ≤2.5μm, ≤10μm, and 2.5–10μm in diameter (PM2.5, PM10, and PMcoarse, respectively); PM2.5 absorbance; nitrogen oxides (NO2 and NOx); traffic intensity; and elemental composition of PM. We estimated cohort-specific associations between breast cancer and air pollutants using Cox regression models, adjusting for major lifestyle risk factors, and pooled cohort-specific estimates using random-effects meta-analyses.

RESULTS

Of 74,750 postmenopausal women included in the study, 3,612 developed breast cancer during 991,353 person-years of follow-up. We found positive and statistically insignificant associations between breast cancer and PM2.5 {hazard ratio (HR)=1.08 [95% confidence interval (CI): 0.77, 1.51] per 5 μg/m3}, PM10 [1.07 (95% CI: 0.89, 1.30) per 10 μg/m3], PMcoarse[1.20 (95% CI: 0.96, 1.49 per 5 μg/m3], and NO2 [1.02 (95% CI: 0.98, 1.07 per 10 μg/m3], and a statistically significant association with NOx [1.04 (95% CI: 1.00, 1.08) per 20 μg/m3, p=0.04].

CONCLUSIONS

We found suggestive evidence of an association between ambient air pollution and incidence of postmenopausal breast cancer in European women. https://doi.org/10.1289/EHP1742.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

Dioxins and related environmental contaminants increase TDP-43 levels

Background

Amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative condition that is characterized by progressive loss of motor neurons and the accumulation of aggregated TAR DNA Binding Protein-43 (TDP-43, gene: TARDBP). Increasing evidence indicates that environmental factors contribute to the risk of ALS. Dioxins, related planar polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that activate the aryl hydrocarbon receptor (AHR), a ligand-activated, PAS family transcription factor. Recently, exposure to these toxicants was identified as a risk factor for ALS.

Methods

We examined levels of TDP-43 reporter activity, transcript and protein. Quantification was done using cell lines, induced pluripotent stem cells (iPSCs) and mouse brain. The target samples were treated with AHR agonists, including 6-Formylindolo[3,2-b]carbazole (FICZ, a potential endogenous ligand, 2,3,7,8-tetrachlorodibenzo(p)dioxin, and benzo(a)pyrene, an abundant carcinogen in cigarette smoke). The action of the agonists was inhibited by concomitant addition of AHR antagonists or by AHR-specific shRNA.

Results

We now report that AHR agonists induce up to a 3-fold increase in TDP-43 protein in human neuronal cell lines (BE-M17 cells), motor neuron differentiated iPSCs, and in murine brain. Chronic treatment with AHR agonists elicits over 2-fold accumulation of soluble and insoluble TDP-43, primarily because of reduced TDP-43 catabolism. AHR antagonists or AHR knockdown inhibits agonist-induced increases in TDP-43 protein and TARDBP transcription demonstrating that the ligands act through the AHR.

Conclusions

These results provide the first evidence that environmental AHR ligands increase TDP-43, which is the principle pathological protein associated with ALS. These results suggest novel molecular mechanisms through which a variety of prevalent environmental factors might directly contribute to ALS. The widespread distribution of dioxins, PCBs and PAHs is considered to be a risk factor for cancer and autoimmune diseases, but could also be a significant public health concern for ALS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-017-0177-9) contains supplementary material, which is available to authorized users.

Polycyclic Aromatic Hydrocarbons In Edible Mushrooms from Niger Delta, Nigeria: Carcinogenic and Non-Carcinogenic Health Risk Assessment

In the oil-rich Niger Delta, hydrocarbon pollution and oil spillages, gas flaring and sundry anthropogenic activities constitute sources of polycyclic aromatic hydrocarbons (PAHs), with food contamination playing a major role in human exposure. In this study we assessed PAH levels in wild and cultivated edible mushroom species consumed by the general population from the oil producing Niger Delta, Nigeria. The concentrations of USEPA-16 PAHs were determined by gas chromatography and carcinogenic and non-carcinogenic health risks were calculated. The concentrations of USEPA-16 PAHs ranged from 0.02 mg/kg – 3.37 mg/kg. The dietary intake of carcinogenic and non-carcinogenic USEPA-16 PAHs (Naphthalene, Acenaphthylene, Acenaphthene, Anthracene, Phenanthrene, Flourene, Flouranthene, Pyrene, Benzo[a]Anthracene, Chrysene, Benzo[a]Pyrene, Benzo[b]Flouranthene, Benzo[K]Flouranthene, Benzo[g, h, i]Perylene, Dibenz[a, h]Anthracene and Ideno[1,2,3-cd]Pyrene) for adults, adolescents and seniors ranged from 0.00 – 0.05 mg/kg/day, 0.00 – 0.06 mg/kg/day and 0.00 – 0.07 mg/kg/day. The BaPeq ranged from 0.02 – 2.76 with margin of exposure MOE values of BaP ranging from 3,500,000 to 700,000, 3,500,000 and 3,500,000 to 7,000,000 for adults, adolescents and seniors indicating very insignificant health risk. The incremental lifetime cancer risk was within the safe range of 1.56x10-8 – 1.73x10-6 with the highest calculated risk found for wild Pleurotus ostreatus mushroom species from the study area.

Long-term trends (1990-2014), health risks, and sources of atmospheric polycyclic aromatic hydrocarbons (PAHs) in the U.S

Polycyclic aromatic hydrocarbons (PAHs) are a category of over 100 various chemicals released from numerous combustion sources. The ubiquity and toxicity of PAHs have posed high health risks on human populations. This study aims to examine the long-term trends of atmospheric PAHs at the national-level in the U.S., and evaluate their cancer risks. Daily concentrations of PAHs measured at 169 monitoring stations between 1990 and 2014 were obtained from the U.S. Environmental Protection Agency's Air Quality System. Temporal trends were examined using generalized linear model with generalized estimating equations. Random-effects analysis of variance was performed to explore variance between regions, sites, years, and months with a hierarchical structure. Source categories were identified using diagnostic ratios. National population level cancer risks were estimated using the relative potency factors and inhalation unit risk method. Ambient PAH concentrations displayed an overall downward trend (6-9% annual reduction) in urban areas, but not in rural areas. Seasonal and weekday/weekend effects were significant. Urban concentrations were twice of the rural level. The between-site variation outweighed the temporal variation, indicating large spatial heterogeneity. The predominant PAH sources were from traffic and non-traffic related fuel combustions with a dominant contribution from diesel emissions. The average excess lifetime cancer risk was estimated to be 9.3 ± 30.1 × 10^-6 (GM: 4.2 × 10^-6) from exposure to ten carcinogenic PAHs. This is the first comprehensive study of the spatiotemporal trends of ambient PAHs at the U.S. national level. The results indicate that future efforts aimed to reduce PAH exposures should focus on diesel emission controls and extending the geographic coverage of air monitoring.

Environmental tobacco smoke exposure and risk of breast cancer in nonsmoking women. An updated review and meta-analysis

CONTEXT

In 2006, we reviewed the evidence on environmental tobacco smoke (ETS) and breast cancer in nonsmoking women. Since then various studies and reviews have been published but opinion remains divided.

OBJECTIVE

To provide an updated review.

METHODS

We extracted study details, derived relative risk (RR) estimates with confidence intervals (CIs) for various ETS exposure indices, and conducted meta-analyses.

RESULTS

The update increased the number of studies from 22 to 47. Using an index for each study most closely equivalent to "spouse ever smoked", a weak but significant association was seen (random-effects RR = 1.15, 95% CI = 1.07-1.23). However, the estimates were heterogeneous: higher for Asian studies than for North American or European studies, higher for studies adjusting for fewer potential confounding variables, and close to 1.0 for prospective studies, regardless of whether or not they asked detailed questions on ETS exposure. The RR for eight prospective studies asking detailed questions was 1.003, 95% CI = 0.96-1.05. Risk was increased in premenopausal women (RR = 1.36, 95% CI = 1.15-1.60), but not postmenopausal women. Dose-response findings were similarly heterogeneous. No significant increase was seen for childhood or workplace exposure, but an increase was seen for total exposure (RR = 1.22, 95% CI = 1.09-1.37).

CONCLUSIONS

Increases mainly derived from case-control studies are prone to recall bias. Study weaknesses and possible publication bias limit interpretation. Considering also the weak association of smoking with breast cancer, and the much lower exposures from ETS than from smoking, our analyses do not clearly demonstrate that ETS exposure increases risk of breast cancer in nonsmokers. More research is needed.

The role of the aryl hydrocarbon receptor in the development of cells with the molecular and functional characteristics of cancer stem-like cells

BACKGROUND

Self-renewing, chemoresistant breast cancer stem cells are believed to contribute significantly to cancer invasion, migration and patient relapse. Therefore, the identification of signaling pathways that regulate the acquisition of stem-like qualities is an important step towards understanding why patients relapse and towards development of novel therapeutics that specifically target cancer stem cell vulnerabilities. Recent studies identified a role for the aryl hydrocarbon receptor (AHR), an environmental carcinogen receptor implicated in cancer initiation, in normal tissue-specific stem cell self-renewal. These studies inspired the hypothesis that the AHR plays a role in the acquisition of cancer stem cell-like qualities.

RESULTS

To test this hypothesis, AHR activity in Hs578T triple negative and SUM149 inflammatory breast cancer cells were modulated with AHR ligands, shRNA or AHR-specific inhibitors, and phenotypic, genomic and functional stem cell-associated characteristics were evaluated. The data demonstrate that (1) ALDH(high) cells express elevated levels of Ahr and Cyp1b1 and Cyp1a1, AHR-driven genes, (2) AHR knockdown reduces ALDH activity by 80%, (3) AHR hyper-activation with several ligands, including environmental ligands, significantly increases ALDH1 activity, expression of stem cell- and invasion/migration-associated genes, and accelerates cell migration, (4) a significant correlation between Ahr or Cyp1b1 expression (as a surrogate marker for AHR activity) and expression of stem cell- and invasion/migration-associated gene sets is seen with genomic data obtained from 79 human breast cancer cell lines and over 1,850 primary human breast cancers, (5) the AHR interacts directly with Sox2, a master regulator of self-renewal; AHR ligands increase this interaction and nuclear SOX2 translocation, (6) AHR knockdown inhibits tumorsphere formation in low adherence conditions, (7) AHR inhibition blocks the rapid migration of ALDH(high) cells and reduces ALDH(high) cell chemoresistance, (8) ALDH(high) cells are highly efficient at initiating tumors in orthotopic xenografts, and (9) AHR knockdown inhibits tumor initiation and reduces tumor Aldh1a1, Sox2, and Cyp1b1 expression in vivo.

CONCLUSIONS

These data suggest that the AHR plays an important role in development of cells with cancer stem cell-like qualities and that environmental AHR ligands may exacerbate breast cancer by enhancing expression of these properties.

Vehicular Traffic-Related Polycyclic Aromatic Hydrocarbon Exposure and Breast Cancer Incidence: The Long Island Breast Cancer Study Project (LIBCSP)

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants, known human lung carcinogens, and potent mammary carcinogens in laboratory animals. However, the association between PAHs and breast cancer in women is unclear. Vehicular traffic is a major ambient source of PAH exposure.

OBJECTIVES

Our study aim was to evaluate the association between residential exposure to vehicular traffic and breast cancer incidence.

METHODS

Residential histories of 1,508 participants with breast cancer (case participants) and 1,556 particpants with no breast cancer (control participants) were assessed in a population-based investigation conducted in 1996-1997. Traffic exposure estimates of benzo[a]pyrene (B[a]P), as a proxy for traffic-related PAHs, for the years 1960-1995 were reconstructed using a model previously shown to generate estimates consistent with measured soil PAHs, PAH-DNA adducts, and CO readings. Associations between vehicular traffic exposure estimates and breast cancer incidence were evaluated using unconditional logistic regression.

RESULTS

The odds ratio (95% CI) was modestly elevated by 1.44 (0.78, 2.68) for the association between breast cancer and long-term 1960-1990 vehicular traffic estimates in the top 5%, compared with below the median. The association with recent 1995 traffic exposure was elevated by 1.14 (0.80, 1.64) for the top 5%, compared with below the median, which was stronger among women with low fruit/vegetable intake [1.46 (0.89, 2.40)], but not among those with high fruit/vegetable intake [0.92 (0.53, 1.60)]. Among the subset of women with information regarding traffic exposure and tumor hormone receptor subtype, the traffic-breast cancer association was higher for those with estrogen/progesterone-negative tumors [1.67 (0.91, 3.05) relative to control participants], but lower among all other tumor subtypes [0.80 (0.50, 1.27) compared with control participants].

CONCLUSIONS

In our population-based study, we observed positive associations between vehicular traffic-related B[a]P exposure and breast cancer incidence among women with comparatively high long-term traffic B[a]P exposures, although effect estimates were imprecise.

CITATION

Mordukhovich I, Beyea J, Herring AH, Hatch M, Stellman SD, Teitelbaum SL, Richardson DB, Millikan RC, Engel LS, Shantakumar S, Steck SE, Neugut AI, Rossner P Jr., Santella RM, Gammon MD. 2016. Vehicular traffic-related polycyclic aromatic hydrocarbon exposure and breast cancer incidence: the Long Island Breast Cancer Study Project (LIBCSP). Environ Health Perspect 124:30-38; http://dx.doi.org/10.1289/ehp.1307736.

Polycyclic Aromatic Hydrocarbons and Breast Cancer: A Review of the Literature

Polycyclic aromatic hydrocarbons (PAHs) exist and persist in the atmosphere due to the incomplete combustion of fossil fuels, and are established human carcinogens. The influence of PAHs on the development of breast cancer, the most commonly diagnosed cancer in women worldwide, remains unclear. As established risk factors only account for approximately 41% of the breast cancer cases in the USA, researchers have sought to uncover environmental factors involved in breast cancer development. The breasts are particularly susceptible to aromatic carcinogenesis, and the implementation of biomarkers has provided promising insights regarding PAH-DNA adducts in breast cancer. The use of biomarkers measuring PAH-DNA adducts assesses exposure to eliminate the bias inherent in self-reporting measures in case-control studies investigating the link between PAHs and cancer. Adduct levels reflect exposure dose as well as how the body responds to this exposure, which is partially attributable to genetic variability. Evidence suggests that exposure to PAHs has a causational effect on breast cancer in humans, yet this interaction is not clearly understood. In vitro and animal-based studies have consistently revealed that exposure to PAHs deleteriously affects breast tissue, but there is no definitive link between these compounds and breast cancer.

Will Women Diagnosed with Breast Cancer Provide Biological Samples for Research Purposes?

BACKGROUND

Little is known about the response rates for biological sample donation and attitudes towards control recruitment, especially in younger women. The goals of this pilot study were to determine in women recently diagnosed with breast cancer, the proportion of cases willing to provide biological samples and for purposes of control recruitment, contact information for friends or colleagues.

METHODS

A population-based sample of breast cancer cases (n = 417, 25-74 years) was recruited from the Ontario Cancer Registry in 2010 and self-administered questionnaires were completed to determine willingness to provide samples (spot or 24-hr urine, saliva, blood) and contact information for friends/colleagues for control recruitment. Using Χ2 analyses of contingency tables we evaluated if these proportions varied by age group (<45 and 45+) and other factors such as ethnicity, education, income, body mass index (BMI), smoking status and alcohol consumption.

RESULTS

Cases were willing to provide blood samples, by visiting a clinic (62%) or by having a nurse visit the home (61%). Moreover, they would provide saliva (73%), and morning or 24-hr urine samples (66% and 52%). Younger cases (≤45) were 3 times (OR) more likely more than older cases to agree to collect morning urine (95% CI: 1.15-8.35). Only 26% of cases indicated they would provide contact information of friends or work colleagues to act as controls. Educated cases were more likely to agree to provide samples, and cases who consumed alcohol were more willing to provide contact information. Ethnicity, income, BMI and smoking had little effect on response rates.

CONCLUSIONS

Reasonable response rates for biological sample collection should be expected in future case controls studies in younger women, but other methods of control selection must be devised.

Long-term exposure to air pollution and mammographic density in the Danish Diet, Cancer and Health cohort

BACKGROUND

Growing evidence suggests that air pollution may be a risk factor for breast cancer, but the biological mechanism remains unknown. High mammographic density (MD) is one of the strongest predictors and biomarkers of breast cancer risk, but it has yet to be linked to air pollution. We investigated the association between long-term exposure to traffic-related air pollution and MD in a prospective cohort of women 50 years and older.

METHODS

For the 4,769 women (3,930 postmenopausal) participants in the Danish Diet, Cancer and Health cohort (1993-1997) who attended mammographic screening in Copenhagen (1993-2001), we used MD assessed at the first screening after cohort entry. MD was defined as mixed/dense or fatty. Traffic-related air pollution at residence was assessed by modeled levels of nitrogen oxides (NOx) and nitrogen dioxide (NO2). The association between mean NOx and NO2 levels since 1971 until cohort baseline (1993-97) and MD was analyzed using logistic regression, adjusting for confounders, and separately by menopause, smoking status, and obesity.

RESULTS

We found inverse, statistically borderline significant associations between long-term exposure to air pollution and having mixed/dense MD in our fully adjusted model (OR; 95% CI: 0.96; 0.93-1.01 per 20 μg/m(3) of NOx and 0.89; 0.80- 0.98 per 10 μg/m(3) of NO2). There was no interaction with menopause, smoking, or obesity.

CONCLUSION

Traffic-related air pollution exposure does not increase MD, indicating that if air pollution increases breast cancer risk, it is not via MD.

Indoor air pollution exposure from use of indoor stoves and fireplaces in association with breast cancer: a case-control study

BACKGROUND

Previous studies suggest that polycyclic aromatic hydrocarbons (PAHs) may adversely affect breast cancer risk. Indoor air pollution from use of indoor stoves and/or fireplaces is an important source of ambient PAH exposure. However, the association between indoor stove/fireplace use and breast cancer risk is unknown. We hypothesized that indoor stove/fireplace use in a Long Island, New York study population would be positively associated with breast cancer and differ by material burned, and the duration and timing of exposure. We also hypothesized that the association would vary by breast cancer subtype defined by p53 mutation status, and interact with glutathione S-transferases GSTM1, T1, A1 and P1 polymorphisms.

METHODS

Population-based, case-control resources (1,508 cases/1,556 controls) were used to conduct unconditional logistic regression to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Breast cancer risk was increased among women reporting ever burning synthetic logs (which may also contain wood) in their homes (OR = 1.42, 95% CI 1.11, 1.84), but not for ever burning wood alone (OR = 0.93, 95% CI 0.77, 1.12). For synthetic log use, longer duration >7 years, older age at exposure (>20 years; OR = 1.65, 95% CI 1.02, 2.67) and 2 or more variants in GSTM1, T1, A1 or P1 (OR = 1.71, 95% CI 1.09, 2.69) were associated with increased risk.

CONCLUSIONS

Burning wood or synthetic logs are both indoor PAH exposure sources; however, positive associations were only observed for burning synthetic logs, which was stronger for longer exposures, adult exposures, and those with multiple GST variant genotypes. Therefore, our results should be interpreted with care and require replication.

Interactions between polycyclic aromatic hydrocarbons in complex mixtures and implications for cancer risk assessment

In this review we discuss the effects of exposure to complex PAH mixtures in vitro and in vivo on mechanisms related to carcinogenesis. Of particular concern regarding exposure to complex PAH mixtures is how interactions between different constituents can affect the carcinogenic response and how these might be included in risk assessment. Overall the findings suggest that the responses resulting from exposure to complex PAH mixtures is varied and complicated. More- and less-than additive effects on bioactivation and DNA damage formation have been observed depending on the various mixtures studied, and equally dependent on the different test systems that are used. Furthermore, the findings show that the commonly used biological end-point of DNA damage formation is insufficient for studying mixture effects. At present the assessment of the risk of exposure to complex PAH mixtures involves comparison to individual compounds using either a surrogate or a component-based potency approach. We discuss how future risk assessment strategies for complex PAH mixtures should be based around whole mixture assessment in order to account for interaction effects. Inherent to this is the need to incorporate different experimental approaches using robust and sensitive biological endpoints. Furthermore, the emphasis on future research should be placed on studying real life mixtures that better represent the complex PAH mixtures that humans are exposed to.

DNA and protein adducts in human tissues resulting from exposure to tobacco smoke

Tobacco smoke contains a variety of genotoxic carcinogens that form adducts with DNA and protein in the tissues of smokers. Not only are these biochemical events relevant to the carcinogenic process, but the detection of adducts provides a means of monitoring exposure to tobacco smoke. Characterization of smoking-related adducts has shed light on the mechanisms of smoking-related diseases and many different types of smoking-derived DNA and protein adducts have been identified. Such approaches also reveal the potential harm of environmental tobacco smoke (ETS) to nonsmokers, infants and children. Because the majority of tobacco-smoke carcinogens are not exclusive to this source of exposure, studies comparing smokers and nonsmokers may be confounded by other environmental sources. Nevertheless, certain DNA and protein adducts have been validated as biomarkers of exposure to tobacco smoke, with continuing applications in the study of ETS exposures, cancer prevention and tobacco product legislation. Our article is a review of the literature on smoking-related adducts in human tissues published since 2002.

Air pollution from traffic and cancer incidence: a Danish cohort study

BACKGROUND

Vehicle engine exhaust includes ultrafine particles with a large surface area and containing absorbed polycyclic aromatic hydrocarbons, transition metals and other substances. Ultrafine particles and soluble chemicals can be transported from the airways to other organs, such as the liver, kidneys, and brain. Our aim was to investigate whether air pollution from traffic is associated with risk for other cancers than lung cancer.

METHODS

We followed up 54,304 participants in the Danish Diet Cancer and Health cohort for 20 selected cancers in the Danish Cancer Registry, from enrolment in 1993-1997 until 2006, and traced their residential addresses from 1971 onwards in the Central Population Registry. We used modeled concentration of nitrogen oxides (NO(x)) and amount of traffic at the residence as indicators of traffic-related air pollution and used Cox models to estimate incidence rate ratios (IRRs) after adjustment for potential confounders.

RESULTS

NO(x) at the residence was significantly associated with risks for cervical cancer (IRR, 2.45; 95% confidence interval [CI], 1.01;5.93, per 100 μg/m(3) NO(x)) and brain cancer (IRR, 2.28; 95% CI, 1.25;4.19, per 100 μg/m(3) NO(x)).

CONCLUSIONS

This hypothesis-generating study indicates that traffic-related air pollution might increase the risks for cervical and brain cancer, which should be tested in future studies.

Lung cancer risk in relation to traffic-related nano/ultrafine particle-bound PAHs exposure: a preliminary probabilistic assessment

Exposures to carcinogenic polycyclic aromatic hydrocarbons (PAHs) have been linked to human lung cancer. The purpose of this study was to assess lung cancer risk caused by inhalation exposure to nano/ultrafine particle-bound PAHs at the population level in Taiwan appraised with recent published data. A human respiratory tract model was linked with a physiologically based pharmacokinetic model to estimate deposition fraction and internal organic-specific PAHs doses. A probabilistic risk assessment framework was developed to estimate potential lung cancer risk. We reanalyzed particle size distribution, total-PAHs, particle-bound benzo(a)pyrene (B[a]P) and PM concentrations. A dose-response profile describing the relationships between external B[a]P concentration and lung cancer risk response was constructed based on population attributable fraction (PAF). We found that 90% probability lung cancer risks ranged from 10(-5) to 10(-4) for traffic-related nano and ultrafine particle-bound PAHs, indicating a potential lung cancer risk. The particle size-specific PAF-based excess annual lung cancer incidence rate due to PAHs exposure was estimated to be less than 1 per 100,000 population, indicating a mild risk factor for lung cancer. We concluded that probabilistic risk assessment linked PAF for limiting cumulative PAHs emissions to reduce lung cancer risk plays a prominent role in future government risk assessment program.