Table 2. Main findings of included studies.
| Author | Year | Findings | Changes |
|---|---|---|---|
| Bassig et al. (16) | 2014 | Longer TL in workers exposed >31 ppm of benzene (1.37±0.23 vs. 1.26±0.17, P=0.03) | Longer |
| Bijnens et al. (17) | 2015 | Doubling the distance to the nearest major road was associated with a 5.32% (95% CI: 1.90 to 8.86%, P=0.003) longer placental TL at birth | Shorter |
| An interquartile increase (22%) in maternal residential surrounding greenness (5 km buffer) was associated with an increase of 3.62% (95% CI: 0.20 to 7.15%, P=0.04) in placental TL | |||
| Bin et al. (18) | 2010 | Coke-oven workers had shorter LTL [1.10±0.75 vs. 1.43±1.06, P=0.026, P (adjust) =0.020] | Shorter |
| Stratification analysis found shorter LTL in male (1.08±0.73 vs. 1.51±1.10, F=9.212, P=0.003) and non-drinking groups (0.96±0.38 vs. 1.26±0.46, F=6.484, P=0.012) | |||
| De Felice et al. (19) | 2012 | TL was shorter in exposed pregnant women (1.27 vs. 3.11, P<0.001) | Shorter |
| hTERT mRNA 28% lower in exposed group (1.123 vs. 1.401, P<0.001) | |||
| TL decreased with increasing the proximity from polluted area (P=0.004) | |||
| Dioni et al. (20) | 2011 | LTL was longer after exposure (1.43±0.51) compared with baseline (1.23±0.28, P<0.001) | Longer |
| Post exposure LTL was positively associated with PM10 (β=0.30, P=0.002) and PM1 (β=0.29, P=0.042) | |||
| hTERT expression was lower (1.31±0.75 vs. 1.68±0.86, P<0.001), but the decrease in hTERT expression did not show a dose-response relationship with PM | |||
| Eshkoor et al. (21) | 2011 | Workers with the mutated genotype (Ile-Val, Val-Val) had shorter TL (0.23±0.35 vs. 1.93±4.53, P=0.008), as well as the workers with wild genotype Ile-Ile (0.30±0.67 vs. 2.65±7.94, P=0.019) | Shorter |
| Hou et al. (22) | 2012 | TL was longer in drivers (0.87, 95% CI: 0.74 to 1.03) than office workers (0.79, 95% CI: 0.67 to 0.93, P=0.001) | Mixed |
| TL increased in association with personal PM2.5 (5.2%, 95% CI: 1.5 to 9.1; P=0.007), personal EC (4.9%, 95% CI: 1.2 to 8.8, P=0.01), and ambient PM10 (7.7%, 95% CI: 3.7 to 11.9; P<0.001) on examination days | |||
| PM10 over the 14 days was associated with shorter TL (−9.9%, 95% CI: −17.6 to −1.5, P=0.02) | |||
| Hoxha et al. (23) | 2009 | Adjusted mean LTL was 1.10 (95% CI: 1.04 to 1.16) in traffic officers and 1.27 in referents (95%CI: 1.20 to 1.35) (P<0.001) | Shorter |
| Traffic officers had shorter LTL within each age category. | |||
| Among traffic officers, adjusted mean relative LTL was shorter in individuals working in high (n=45, LTL = 1.02, 95% CI: 0.96 to 1.09) compared to low traffic intensity (n=32, LTL =1.22, 95% CI: 1.13 to 1.31) (P<0.001) | |||
| LTL decreased with increasing levels of personal exposure to benzene (P=0.004) and toluene (P=0.008) | |||
| Lee et al. (24) | 2017 | Inverse linear relationship was found between ambient PAHs exposure and TL. Each 1 ng/m3 increase in PAH456 with a decrease of −0.14 units (95% CI: −0.25 to −0.11, P=0.01) in TL | Shorter |
| Li et al. (25) | 2015 | Welders and controls did not differ in RTL (P=0.090) | Shorter |
| Every working year as a welder was associated with 0.0066 units shorter TL (95% CI: −0.013 to −0.00053, P=0.033) | |||
| Li et al. (26) | 2011 | N-nitrosamines exposure lead to telomere shortening [measured (n=60) N-nitrosamines β-coefficient =−10 (95% CI: −17 to −1.9) P=0.016; estimated (n=157) N-nitrosamines β-coefficient =−5.3, (95% CI: −9.5 to −0.97) P=0.016] | Shorter |
| Lin et al. (27) | 2017 | Shortest LTL (0.70±0.17) was found in participants who were exposed to combusted solid fuel for three decades. Accumulative effect of cooking fuel usage was inversely correlated with LTL (β=−0.07 95% CI: −0.13 to −0.02, P=0.01) | Shorter |
| Lin et al. (28) | 2013 | Placental cadmium concentration was negatively correlated with placental TL (r=20.138, P=0.013) | Shorter |
| No significant correlation between placental lead concentration and placental TL (r=0.027, P=0.639) | |||
| Ling et al. (29) | 2016 | Urinary 1-OHPyr (β=−0.385, 95% CI: −0.749 to −0.021, P=0.038) and 1-OHNap (β=−0.079, 95% CI: −0.146 to −0.011, P=0.023) were inversely associated with STL which remained after adjusting for confounders | Shorter |
| McCracken et al. (30) | 2010 | IQR increase in annual BC (0.25 µg/m3) was associated with 7.6% decrease (95% CI: –12.8 to –2.1) in LTL | Shorter |
| Pavanello et al. (31) | 2010 | Coke-oven workers had shorter TL (P=0.038) | Shorter |
| Years of work in cokery (P=0.008) and p53 hypomethylation (P=0.001) were the principal determinants of shorter TL | |||
| Pawlas et al. (32) | 2015 | Relative TL shorter in higher Pb group [0.99 (0.63–2.09) vs. 1.18 (0.49–2.06), P=0.008] | Shorter |
| B-Pb was significantly inversely associated with rTL in the children | |||
| Pieters et al. (33) | 2015 | 5 µg/m3 increasing in annual PM2.5 was associated with a decrease of 16.8% (95% CI: −26.0% to −7.4%, P=0.0005) in TL | Shorter |
| Shan et al. (34) | 2014 | High exposed women had 43% shorter TL (95% CI: −113, 28); high 3.3±2.3 vs. low 5.4±−4.5, P=0.19 | Shorter |
| Walton et al. (35) | 2016 | Increase in annual NOx [model coefficient 0.003, (95% CI: 0.001 to 0.005), P<0.001], NO2 [0.009 (0.004, 0.015), P<0.001], PM2.5 [0.041, (0.020, 0.063), P<0.001] and PM10 [0.096 (0.044, 0.149), P<0.001] were associated with increased TL | Longer |
| Ward-Caviness et al. (36) | 2016 | BC was inversely associated with TL in men (β=−0.28, 95% CI: −0.47, −0.08, P=0.005) | Shorter |
| Wong et al. (37) | 2014 | Each 1 mg/m3/h increase in cumulative PM2.5 with a decrease in relative TL of –0.04 units | Shorter |
| Wu et al. (38) | 2012 | Shorter LTL in workers with abnormal BLL and/or ULL (1.66±0.63 vs. 1.91±0.46, P=0.010) | Shorter |
| LTL was in negative correlation with BLL, ULL, working length and body mass index | |||
| LTL has strong inverse correlation with BLB (r=−0.70, P<0.0001) in those with abnormal BLL and ULL | |||
| Xia et al. (39) | 2015 | Non-significant association between short-term PM exposure with TL in type 2 diabetes patients | No change |
| Zota et al. (40) | 2015 | The highest and lowest quartiles of blood and urine cadmium were associated with −5.54% (95% CI: −8.70, −2.37) and −4.50% (95% CI: −8.79, −0.20) shorter LTLs, with dose-response relationship (P for trend <0.05). There was no association between blood lead and LTL | Shorter |
1-OHNap, 1-hydroxynapthalene; 1-OHPyr, 1-hydroxypyrene; 95% CI, 95% confidence intervals; BC, black carbon; BLB, body lead burden; BLL, lead levels in blood; EC, elemental carbon; hTERT, Human Telomerase Reverse Transcriptase; IQR, interquartile range; LTL, leukocyte telomere length; mtDNA, mitochondrial DNA; PAHs, polycyclic aromatic hydrocarbons; Pb, Lead; PM, particulate matter; STL, sperm telomere length; TL, telomere length; ULL, lead levels in urine.