Lifetime Cancer Risk Assessment Research Articles

Appraisal of microplastic pollution and its related risks for urban indoor environment in Bangladesh using machine learning and diverse risk evolution indices

The widespread presence of Microplastics (MPs) is increasing in the indoor environment due to increasing annual plastic usage, which is becoming a global threat to human health. Therefore, this is the first research in Bangladesh to identify, and characterize, MP pollution and its allied threats to human health in the indoor urban environment, where 80 household dust samples were collected from the whole study area. The presence of MPs in household dust of the urban indoor environment was 25.8 ± 6.43 particles/g with a significant variety, whereas the fiber shape (73%), 0.5–1.00 mm ranged MPs size (58%), blue color (21%), and polystyrene polymer (34%) was the most ubiquitous MPs category. The pollution load index (1.61–2.96) indicated significant pollution due to the high abundance of MPs. Besides, other risks evaluating indices including contamination factor (1.00–3.51), and Nemerow pollution index (1.60–3.51) represent moderate to high MP-induced pollution. The polymer hazard index (119.54 ± 70.34) indicated significant risks for the selected polymers to the indoor environment living inhabitants. Machine learning approaches, especially random forest and support random vector machine were effective in predicting the number of MPs, where EC, salinity, pH, OC, and texture classes acted as controlling factors. Children and adults might be ingesting 4.12 ± 1.01 and 2.27 ± 0.57 particles/day through the ingestion exposure route, which has significant health effects. Polymer-associated lifetime cancer risk assessment results show that there are moderate risks for both adults and children, but children tend to be more susceptible to MP risks. The overall study found that Dhaka was the most severely MPs induced risky division among the others. This study reveals that high quantities of MPs in indoor environments could pose a serious health hazard' to different exposure groups.

Ecological risk of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in the sediment of a protected karst plateau lake (Caohai) wetland in China

Understanding PAH and OCP distributions and sources in lakes is necessary for developing pollutant control policies. Here, we assessed the occurrence, risk, and sources of PAHs and OCPs in the sediment of Caohai Lake. The PAHs were predominantly high-molecular-weight compounds (mean 57.5 %), and the diagnostic ratios revealed that coal, biomass burning, and traffic were the sources of PAHs. HCHs (6.53 ± 7.22 ng g−1) and DDTs (10.86 ± 12.16 ng g−1) were the dominant OCPs and were primarily sourced from fresh exogenous inputs. RDA showed that sediment properties explained 74.12 % and 65.44 % of the variation in PAH and OCP concentrations, respectively. Incremental lifetime cancer risk (ILCR) assessment indicated that hazardous PAHs in Caohai Lake sediment posed moderate risks to children and adults (ILCR>1.0 × 10−4), while the risk from OCPs was low; however, the recent influx of HCHs and DDTs requires additional attention.

Characterization and health risk assessment of PM2.5-bound polycyclic aromatic hydrocarbons in Yangon and Mandalay of Myanmar

To better understand the potential adverse health effects of atmospheric fine particles in the Southeast Asian developing countries, PM2.5 samples were collected at two urban sites in Yangon and Mandalay, representing coastal and inland cities in Myanmar, in winter and summer during 2016 and 2017. The concentrations of 21 polycyclic aromatic hydrocarbons (PAHs) in PM2.5 were determined using a gas chromatography–mass spectrometry (GC–MS). The concentrations of PAHs in PM2.5 in Yangon and Mandalay ranged from 7.6 to 180 ng m−3, with an average of 72 ng m−3. The PAHs were significantly higher in winter than in summer, and significantly higher in Mandalay than in Yangon. The health risk analysis of PAHs, based on the toxic equivalent quantity (TEQ) calculation, and the incremental lifetime cancer risk (ILCR) assessment indicated that PM2.5 in Myanmar has significant health risks with higher health risks in Mandalay compared to Yangon. Diagnostic ratios of PAHs, correlation of PAHs with other species in PM2.5 and the positive matrix factorization (PMF) analysis showed that TEQ is strongly affected by biomass burning and vehicular emissions in Myanmar. Additionally, it was found that the aging degree of aerosols and air mass trajectories had great influences on the concentration and composition of PAHs in PM2.5 in Myanmar, thereby affecting the toxicity of PM2.5.

Concentration and sources of persistent organic pollutants within the vicinity of a scrap-iron smelting plant: Seasonal pattern and health risk assessment

Polychlorinated biphenyls (PCBs) are a class of ubiquitous and significant synthetic organic chemicals that pose deleterious threats to the environment and human health. This study examined the concentration, indoor-outdoor and seasonal change, sources, and health effects of PCBs in particulate-bound dust near a scrap iron recycling plant. PCBs levels were determined in samples using gas chromatograph mass spectrometer. The results indicated that 5 Cl atoms PCB constituted the majority of PCBs (41% overall), contributing 43% during the rainy season and 39% during the dry season. Dioxin-like PCBs (DLPCBs) contributed 38% during the rainy season and 33% during the dry season. In addition, DLPCB accounted for 26% and 40% of indoor and outdoor PCB emissions, respectively. Iron and steel production were identified as the highest identified contributing sources, accounting for 76% of PCB emissions in the rainy season, while plastic combustion had the highest contribution in the dry season, accounting for 44% of PCB emissions. Incremental Lifetime Cancer Risk assessment showed ingestion as the main exposure pathway for children and adults during the two seasons (74.42% and 58.24%, respectively), followed by dermal exposure, while inhalation had the least contribution. A multifaced approach involving relevant agencies, the industry, and the community is required to reduce exposure.

Assessment of radiation dose level and excess lifetime cancer risk associated with dust samples collected from selected nursery and primary schools in Ife Central and Ife East, Osun State, Nigeria.

Abstract Primordial radionuclides are, among others, sources of radiation exposure to man. In this study, dust from some 24 nursery and primary schools in Ife Central and Ife East Local Government Areas (LGA) of Osun State were collected and analysed for 238U, 232Th, and 40K using CsI scintillation detector connected to a Universal Radiation Spectrum Analyser (URSA II) for spectrum analysis. From the specific activity concentrations of 238U, 232Th, and 40K, absorbed dose rates and radiological parameters were calculated. The mean activity concentrations of 238U, 232Th, and 40K in Bq/kg were found to be (45±2, 46±2), (56±5,60±5) and (669±76, 744±86) respectively for Ife Central and Ife East LGAs, however, the difference between the data sets from the two communities were not statistically significant. The total mean ± S.D (standard deviation) calculated over the whole study area were as follows; 238U= 45±11; 232Th=58±15 and 40K=702±196. The values of these radionuclides’ activities were higher than the world averages of 33, 45, and 420 for 238U, 232Th, and 40K respectively set by UNSCEAR. The mean absorbed dose rate in the air (in nGy/h) for Ife Central was 85±7 while for Ife East was 92±8. Both values were higher than the world average of 55 nGy/h. Also, the excess lifetime cancer risk was 1.66 × 10-3 for Ife Central and 1.8 × 10-3 for Ife East LGAs. Generally, Ife East LGA has higher activity concentrations than Ife Central LGA although the difference is not statistically significant.

Biomonitoring and Biomathematical Modeling of Health Risks Associated with Dumpsite Grown Vegetables in Lagos State.

Conversion of dumpsites to farm lands in several communities is a usual practice in Nigeria. Wastes accumulate heavy metals in a variety of forms. This study assessed the concentration, degrees of contamination, and attendant health risk of heavy metals (HMs), using two major indigenous vegetables (Amaranthus viridis and Talinum triangulare) grown on five major dumpsites in Lagos state. After wet digestion, the mean concentrations of the HMs in the vegetable samples were evaluated using atomic absorption spectrophotometer (AAS). Daily intake of metals (DIM), target hazard quotient (THQ), and hazard index (HI) biomathematics were employed in the assessment of non-carcinogenic health risk. Incremental lifetime cancer risk (ILCR) assessment was used to assess carcinogenicity. The obtained result shows that the concentrations of HMs fell within the following ranges: (0.37 to 0.59), (0.07 to 1.36), (0.30 to 1.92), (0.00 to 0.03), and (0.00 to 0.04) mg/kg; for zinc (Zn), lead (Pb), Iron (Fe), cadmium (Cd), and chromium (Cr), respectively, with low to moderate variability. At Ikorodu dumping site, the Pb concentration was above the World Health Organization (WHO) permissible range and has the highest contamination factor. DIM for Pb was also above threshold values (> 1) in both adults and children, while the THQ values for Fe, Pb, and Cd were above 1 (> 1) in both adults and children. HI values for the vegetables exceeded WHO normal range (> 1), except Abule-Egba dumps' samples (70% HI greater than 1 in adults and 90% HI greater than 1 in children). Additionally, the ILCR values of above 50% of the samples were above the WHO (10-6) limits, with the highest value in children (Cd, 1.064 × 10-3) indicating high risk of carcinogenicity over a life time of exposure. Thus, the results revealed great health risk from consumption of vegetables from the four major dumping sites, with children being at greater risk.

Direct gamma dose rate measurement and assessment of excess lifetime cancer risk.

In this study, in some neighborhoods in Kahramanmaraş province of Turkey, indoors and outdoors direct gamma dose rate measurements have been done. All of the gamma dose rate measurements have been made at ground level and at the height of 1m from the ground. The median values of the gamma dose rates on the ground and 1m above the ground indoors are 70.34±7.74 and 49.53±5.39nGy h-1, respectively. Outdoor measurements have been carried out on both soil and asphalt floors. The average values of gamma dose rate on the ground and at a height of 1m outdoors (soil floor) are 68.16±7.49 and 53.50±5.88nGy h-1, respectively. The mean values of gamma dose rate on the ground and 1m above the ground outdoors (asphalt floor) are 61.63±6.77 and 48.69±5.35nGy h-1, respectively. Indoor and outdoor average gamma dose rates are below the mean world. In addition, using the measured gamma dose rate values, annual effective dose equivalent (AEDE) and excess lifetime cancer risk (ELCR) for adults have been calculated. The total AEDE and ELCR (on soil floors and indoors at 1m above ground level) are 0.31±0.03mSv y-1 and 1.08±0.10×10-3, respectively. The total AEDE and ELCR (on asphalt floors and indoors at 1m above ground level) are 0.30±0.03mSv y-1 and 1.06±0.10×10-3, respectively. The AEDE and ELCR for adults living in the neighborhoods within the scope of the study in Kahramanmaraş city center within 1y are lower than the average world.

Investigation on the Quality of Prolonged Storage of Packaged Water Commonly Produced in North Central, Nigeria

This study investigated the effects of prolonged storage conditions on the physicochemical parameter, toxic metals, microbial loads, and health risks assessment of randomly selected three brands of sachet and bottled water in North Central, Nigeria. One hundred eighty samples of water brands (sachet and bottled) were collected from 10 different factories and were grouped into three. They were analyzed immediately (initial), being exposed to mild sunlight (stored with a container) and exposed to intense sunlight (stored without a container) conditions for six weeks. The results of the physicochemical parameters (sachet and bottle) were within the limits set by the World Health Organization (WHO) and the Standard Organization of Nigeria (SON). While the results of heavy metals analysis for both sachet and bottled water recorded 0.15 - 0.51 mg/L (0.10 mg/L , 0.05 mg/L), 0.13 - 0.38 mg/L (0.015 mg/L, 0.01 mg/L) and 0.55 - 1.11 mg/L (0.03 mg/L, 0.3 mg/L) for Chromium (Cr), Lead (Pb) and Iron (Fe) respectively, as compared to the permissible limits (values in the bracket for each heavy metals) set by WHO and SON. The microbial analysis results ranged between 6.58 - 124.51 Cfu/100 mL, 0.52 - 37.56 Cfu/100 mL, 0.07 - 5.00 Cfu/100 mL, 0 - 2.07 Cfu/100 mL for Total Bacteria Count (TBC), Total Coliform Count (TCC), Faecal Coliform Count (FCC) and Total Fungal Count (TFC) respectively, which showed no effective quality control system. Incremental lifetime cancer risk (ILCR) assessment revealed a carcinogenic health risk to the populace drinking this water. The study concludes that water stored under sunlight for a long period is not good for human consumption and therefore adequate monitoring by the appropriate agencies is emphasized.

Potential microbial mechanisms underlying the effects of rising atmospheric CO2 levels on the reduction and methylation processes of arsenic in the paddy soil

Many studies have demonstrated that climate change affects the biogeochemical cycle of pollutants, but the mechanisms of arsenic (As) biogeochemical processes under high CO2 levels are unknown. Here, rice pot experiments were carried out to explore the underlying mechanisms of the impacts of elevated CO2 on the reduction and methylation processes of As in paddy soils. The results revealed that elevated CO2 might increase As bioavailability and promote As(V)-to-As(III) transformation in the soil as well as higher As(III) and dimethyl arsenate (DMA) accumulation in rice grains, thus increasing health risk. In As-contaminated paddy soil, two key genes involved in the biotransformation of As (arsC and arsM) and associated host microbes were identified as being significantly promoted by increasing CO2 levels. Elevated CO2 enriched the soil microbes harboring arsC (Bradyrhizobiaceae and Gallionellaceae), which aided in the reduction of As(V) to As(III). Simultaneously, elevated CO2 enriched soil microbes harboring arsM (Methylobacteriaceae and Geobacteraceae), allowing As(V) to be reduced to As(III) and then methylated to DMA. The findings of the Incremental Lifetime Cancer Risk (ILTR) assessment suggested that elevated CO2 exacerbated the individual adult ILTR from rice food As(III) consumption by 9.0 % (p < 0.05). These findings show that elevated CO2 aggravates the exposure risk of As(III) and DMA in rice grains by changing microbial populations involved in As biotransformation in paddy soils.

Concentration level, health risk assessment and source apportionment of nitrosamines in PM2.5 in Urumqi during winter time

Nitrogen-containing organic compounds (NOCs) in atmospheric particulate matter are important species for the formation of brown carbon. N-nitrosamines are a class of NOCs which are carcinogenic to humans. In this paper, nine nitrosamines of PM2.5 were analyzed by gas chromatography-tandem triple quadrupole mass spectrometry (GC-MS/MS) in a multiple reaction monitoring (MRM) mode in Urumqi, Xinjiang. The aim is to reveal the concentration level, assess the carcinogenic risk and identify the possible emission source of nitrosamines during winter time. The results show that total nitrosamine concentrations range from 1.54 to 23.22 ng m−3, with a daily average of 4.47 ng m−3. N-nitrosodimethylamine (NDMA), N-nitrosodi-n-butylamine (NDBA), N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR) and N-nitrosodiphenylamine (NDPhA) are predominant compounds for more than 80% of the total nitrosamines. The average concentrations of nitrosamines in each carcinogenic classification are 2.68, 1.45, and 0.34 ng m−3, respectively. Cumulative lifetime cancer risk assessment indicates that adult exposure to nitrosamine concentrations of 1 h per day results in 1.15 excess cancer cases per million population. Furthermore, based on correlation analysis and Positive Matrix Factorization, NDMA and NDBA may from disinfection process for water treatment, landfills, cooking and vehicle exhaust; NPYR and NDEA may be mainly emitted from cooking and tobacco combustion. However, NDPhA presents a negative correlation with other nitrosamines, probably resulting from the atmospheric reaction source. These findings not only draw attention to the systematic research of nitrosamines in PM2.5 but also provide a new perspective on the monitoring and management of regional air pollutants.

Health Risk Assessment of PAHs from Estuarine Sediments in the South of Italy

Increased concerns about the toxicities of Polycyclic Aromatic Hydrocarbons (PAHs), ubiquitous and persistent compounds, as well as the associated ecotoxicology issue in estuarine sediments, have drawn attention worldwide in the last few years. The levels of PAHs in the Sele, Sarno, and Volturno Rivers sediments were evaluated. Moreover, the cancerogenic risk resulting from dermal and ingestion exposure to PAHs was estimated using the incremental lifetime cancer risk (ILCR) assessment and the toxic equivalent concentration (TEQBaP). For Sele River, the results showed that the total PAH concentration ranged from 632.42 to 844.93 ng g-1 dw, with an average value of 738.68 ng g-1 dw. ∑PAHs were in the range of 5.2-678.6 ng g-1 dw and 434.8-872.1 ng g-1 dw for the Sarno and Volturno River sediments, respectively. The cancerogenic risk from the accidental ingestion of PAHs in estuarine sediments was low at all sampling sites. However, based on the ILCRdermal values obtained, the risk of cancer associated with exposure by dermal contact with the PAHs present in the sediments was moderate, with a mean ILCRdermal value of 2.77 × 10-6. This study revealed the pollution levels of PAHs across the South of Italy and provided a scientific basis for PAH pollution control and environmental protection.

Excess lifetime cancer risk assessment of radiographers at some radiography facilities in Warri, Delta state

Excess lifetime cancer risk assessment of radiographers at some radiography facilities in Warri, Delta state

Environmental Gamma Radiation Measurement, Dose Rate and Lifetime Cancer Risk Assessment in Malatya Province and its Districts

Bu çalışmada, Malatya ilinde, 15 farklı noktada, gama doz hızı ölçümleri yapılmıştır. Ölçümler, her noktada hem yerde hem de yerden 1 m yükseklikte alınmıştır. Gama doz hızı ölçümleri NaI (Tl) kristaline sahip taşınabilir bir sintilasyon sayacı kullanılarak yapılmıştır. Gama doz hızlarına (DR) ek olarak, yıllık etkin doz oranları (YEDO) ve ömür boyu kanser riski (ÖBKR) değerleri de hesaplanmıştır. Yerden 1 m yükseklikte DR, YEDO ve ÖBKR için elde edilen ortalama değerler, sırasıyla, 48,47 nGy/h, 58,18 µSv/y ve 0,2110-3 olarak hesaplanmıştır. Bu çalışmada sunulan sonuçlar, Türkiye’nin farklı bölgelerinde yapılan benzer çalışmaların sonuçları ve UNSCEAR tarafından verilen dünya ortalama değerleri ile karşılaştırılmıştır.

Distribution Characteristics and Potential Risks of Polycyclic Aromatic Hydrocarbon (PAH) Pollution at a Typical Industrial Legacy Site in Tianjin, North China

Polycyclic aromatic hydrocarbon (PAH) pollution in the soil of industrial legacy sites is a prominent problem when reusing urban land. To estimate the potential risks of PAHs, this study investigated 16 priority PAHs in the soil at different depths in a typical decommissioned industrial site in Tianjin. PAH concentrations were determined via gas chromatography-(tandem) quadrupole mass spectrometry. Incremental lifetime cancer risk (ILCR) assessment was applied to assess the potential risks to the population after land reconstruction. The total concentrations of PAHs in the soil at different depths ranged from 38.3 ng·g−1 to 1782.5 ng·g−1, which were below the risk control standard for soil contamination of development land (GB 36600-2018). Low-ring (two-three ring) PAHs exhibit a dominant component, and the variations in PAH compositions were closely related to the former production units and soil properties. Compared to silty clay layers, PAHs tended to accumulate in the permeable miscellaneous fill layers. Incremental lifetime cancer risk assessment values associated with different exposure pathways for children, adolescents, and adults were calculated. The results showed potential carcinogenic risks for people of varying ages in this area, but they were still acceptable. In general, this legacy site can meet the demands of sustainable land development.

Potential health risk estimation of naturally occurring radionuclides intake due to the consumption of seafood around Coastal zone

As part of a regional baseline study, the distribution of naturally occurring radioactive materials in the marine fish diversity consumed by different age group representatives living in the Kalpakkam coastal zone was studied. The average activity of natural radionuclide in 238U, 232Th, and 40K (n = 40) was 28.51, 239.58, and 118.95 Bq kg-1, respectively. The annual dose of ingestion, lifetime carcinogenic risk assessment and cancer risk assessment due to 238U, 232Th, and 40K were estimated by marine fish diversity in children aged 1-4,5-9,10-14,15-17 years, adults, pregnant women, and the fishing community. The Hospital-Based Cancer Registry (HBCR) compares to the coastal zone. Statistical studies such as Pearson correlation analysis, Principle component analysis, and Cluster analysis report check that the current levels of natural radionuclide do not pose a significant radioactivity threat to the residents based on the activity of the radionuclide.

Pollution, source and risk assessment of PAHs in Chinese tea

In this study, multi-walled carbon nanotubes continuous solid-phase extraction (MWCNTs-CSPE) combined with high-performance liquid chromatography in series with ultraviolet and fluorescence dual detectors (HPLC-DAD-FLD) approach were employed to investigate the concentration, source, and risk of 22 PAHs from Chinese tea products, classified and analyzed seven major categories and 28 varieties of 119 tea samples. The results found that the pollution degree of different varieties of tea is different, and the total concentration range of Σ22 PAHs is 136.99–462.51 μg/kg, in which ΣPAH4 (BaA, CHR, BbF, BaP) ranges from 37.64 to 106.90 μg/kg, ∑16 EPA PAHs is 136.99–440.82 μg/kg. PAHs are mainly composed of 2–4 rings. PAHs characteristic parameter analysis shows that PAHs in Chinese tea products are mainly from fuel oil, wood burning, coal and oil combustion. Benzo[a]pyrene always plays an important role in the carcinogenicity of samples. Lifetime cancer risk assessment showed that black tea had a higher cancer risk level which was 3.75 × 10−7–2.31 × 10−6. The cancer risk of ILCR increases with age, older adults have a higher lifetime cancer risk than younger children, and females have a higher lifetime cancer risk than males, but it can be ignored.

Contamination level, sources, and health risk of polycyclic aromatic hydrocarbons in suburban vegetable field soils of Changchun, Northeast China

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants. With the expansion of the city, the suburban environment is being increasingly polluted by PAHs, which pose a huge potential risk for suburban agriculture. Therefore, we conducted a survey focusing on the pollution level, sources, and risk of PAHs in Changchun suburban vegetable soils, Northeast China. The total concentrations of 16 PAHs (Σ16PAHs) in soils were between 2338.2 and 15,200 ng g−1 (mean 6778.1 ng g−1), which were significantly higher than those in most other cities. High molecular weight PAHs were the major components, which occupied over 85.63% of all PAHs. Seven potential carcinogenic PAHs accounted for 56.96% of the Σ16PAHs. Source apportionment results based on the ratio of PAH isomers and principal components analysis showed that PAHs were primarily derived from pyrolysis sources, such as biomass/coal combustion, traffic emissions, and petroleum. Ecological risk values of PAHs were between effects range-low (ERL) and effects range-median (ERM), which might cause occasionally ecological risks in the suburbs. According to the incremental lifetime cancer risk assessment results, the health risks to the exposed population were in the acceptable level, with dermal contact and ingestion being the predominant exposure pathway.

Assessment of Annual Effective Dose and Excess Lifetime Cancer Risk in Grain Samples Collected from Kerbala Governorate, Iraq

Assessment of Annual Effective Dose and Excess Lifetime Cancer Risk in Grain Samples Collected from Kerbala Governorate, Iraq

222Rn Activity Concentration Measurement and its Radiological Risks in the Environment of Barserin Village, Erbil-Iraq

222Rn Activity Concentration Measurement and its Radiological Risks in the Environment of Barserin Village, Erbil-Iraq

Determination of phthalate acid esters (PAEs) in bottled water distributed in tehran: a health risk assessment study

ABSTRACT In this study, the levels of six PAEs [bis (2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), diethyl phthalate (DEP), dimethyl phthalate (DMP) and di-n-octyl phthalate (DNOP)] were determined from four types of bottled water)non-carbonated, mineral, carbonated and carbonated flavoured) using MSPE method (magnetic solid phase extraction) and GC/MS technique (gas chromatography/mass spectrometry). The mean concentration of total PAEs was 6.11 ± 1.43 µg/L. The mean concentration of DEHP was 2.22 ± 0.76 µg/L and was lower than the United States Environmental Protection Agency (USEPA) standard level in drinking water (6 μg/L for DEHP). The highest mean level of total PAE was observed in carbonated water (7.43 ± 2.03 μg/L) and the lowest mean level of total PAE was observed in non-carbonated water (5.15 ± 0.41 μg/L). The Monte Carlo method was applied to calculate the Target Hazard Quotient (THQ), Chronic Daily Intake (CDI), and Incremental Life Cancer Risk (ILCR) indexes. In all samples, the rank order of the estimated THQ values based on the 95% percentile was DEHP (4.77E-4) > DBP (2.25E-5) > BBP (1.99E-5) > DEP (2.75E-6) and there would be unlikely non-carcinogenic risks for consumers (THQ<1). The incremental lifetime cancer risk assessment revealed that phthalate esters (DEHP) in evaluated bottled water samples did not pose a serious concern to humans.