Table III. Cross-Sectional Prevalence of Respiratory Morbidity Among Cohorts Exposed to Styrene.

Reference	Industry	No. workers	Symptoms or diagnoses	Findings	Strength of evidencea
Strong, intermediate, or suggestive evidence
Chmielewski and Renke [1975]	Not reported	122	Cough	(i) Chronic cough: 4 (4%) of 101 with short tenure (mean 1 year) and 3 (15%) of 21 with long tenure (mean 10 years); (ii) long-tenured workers: 1 (5%) had chronic bronchitis, 2 (10%) had CXRs that showed “intensified lung structure and fine macular mottling,” and 4 (19%) had FEV1/FVC of 57.1–68.1%	+
Lorimer et al. [1976, 1978]	Styrene manufacturing	488	Wheezing, chest tightness	(i) Wheezing or chest tightness from styrene vapors: 7% (low-exposure), 19% (high-exposure), P < 0.001; (ii) recurrent wheeze or chest tightness: 5% (low-exposure), 12% (high-exposure), P < 0.01; (iii) acute lower respiratory symptoms for workers with low versus high exposure: 6%, 12%, NS (0.1–7.0 years of exposure); 8%, 25%, P < 0.02 (7.1–20.0); 8%, 18%, P < 0.05 (>20.0); (iv) percentage non-smokers with FEV1/FVC <0.75: 41.4% (with detectable urinary mandelic acidb), 21.0% (with non-detectable urinary mandelic acid), P < 0.05	++
Harkonen [1977]	Polyester plastic manufacturing	98	Shortness of breath, chronic bronchitis	(i) Frequency of shortness of breath during workday (exposed/unexposed): never (67%/84%); sometimes (30%/13%); often (3%/3%), P < 0.05; (ii) frequency of chronic bronchitis (exposed/unexposed): 28%/12%, P < 0.05, smoking habits did not differ between exposed and unexposed; (iii) 43 subjects had normal FEV1 and FVC measurements (values not provided)	++
Jedrychowski [1982]	Styrene, methyl methacrylate manufacturing	1,137	Asthmatic symptoms, chronic bronchitis	(i) Chronic bronchitis and/or asthma symptoms: 17.8% (exposed) and 19.5% (controls); (ii) FEV1 <80% of predicted: 45.4% (exposed) and 18.0% (controls), P < 0.05; (iii) RR for FEV1 <80% of predicted, 4.7 (95% CI, 2.4–7.0) for exposed non-smokers/ex-smokers compared with unexposed non-smokers/ex-smokers	++
Jedrychowski and Fonte [1984]	Chemical manufacturing	4,717	Bronchial asthma, chronic bronchitis	(i) Workers in one styrene department (observed/expected): asthma/no chronic bronchitis (26/17.7, P < 0.05); asthma/chronic bronchitis (16/9.0, P < 0.05); (ii) obstructive syndrome (observed/expected): department V, 38.0%/52.4%, NS; department VI, 68.0%/35.7%, P < 0.05	+++
Robins et al. [1990]	Patterns and models manufacturing	864	Chronic bronchitis, dyspnea, wheezing	(i) 199 workers known to work most often with plastic; (ii) 10-year increase in plastic-years associated with OR for wheezing, 1.49 (P = 0.04); chronic bronchitis, 1.65 (P = 0.019); dyspnea, 2.23 (P = 0.0004); (iii) no significant change in FEV1, FVC, FEV1/FVC associated with plastic-years or polyester/styrene-years of exposure	++
CDC [1992]	Yacht manufacturing	44	Cough, dyspnea, chest tightness	(i) Air samples 1.0–120.4 ppm; (ii) symptoms: cough, 13 (35%) of 37; dyspnea, 5 (14%) of 36; chest tightness and difficulty breathing, 22 (59%) of 37; (iii) spirometry: obstructive pattern, 4 (10%) of 39; restrictive pattern, 2 (5%); (iv) no relationship detected between exposure to air styrene concentrations >25 ppm and pulmonary function measurements	+
Lewin-Kowalik et al. [1994]	Chemical manufacturing	647	Not reported	(i) Mean FEV1 among non-smoking males compared with normal values: 2.85 L/3.54 L, P = 0.003 (styrene department) and 2.82 L/3.52 L, P < 0.003 (polystyrene department); (ii) mean FVC among nonsmoking males compared with normal values: 3.70 L/4.46 L, P < 0.02 (styrene department) and 3.89 L/4.26 L, P < 0.05 (polystyrene department)	++
Tucek et al.[2002]	Acrylic acid esters manufacturing	1,005	Upper respiratory symptoms, cough	(i) 280 workers exposed to styrene; (ii) work-related respiratory symptoms (e.g., mucous membrane irritation, cough): exposed, 40%; controls, 20%; (iii) for both smokers and non-smokers, no significant differences in spirometric parameters for exposed versus controls	+
Oner et al. [2004]	Furniture manufacturing	47	Chest tightness, cough, dyspnea, wheezing	(i) 5 (11%) workers with dyspnea, wheezing, chest tightness, or dry cough associated with styrene exposure; (ii) 3 of these 5 workers with occupational respiratory symptoms had positive methacholine challenges; of these 3 workers, 1 had improvements in PEF when away from work and 0 had positive inhalation challenge to styrene	+
Sati et al. [2011]	Plastics manufacturing	64	Not reported	(i) Mean FEV1: 2.60 L (exposed) and 3.11 L (controls), P < 0.001; (ii) mean FVC: 2.90 L (exposed) and 3.67 L (controls), P < 0.001; (iii) mean FEV1/FVC percentage: 89.3% (exposed), 85.5% (controls), P = 0.082; (iv) mean FEF25–75%: 3.02 L/s (exposed) and 3.28 L/s (controls), P = 0.31	++
Helal and Elshafy [2013]	Plastics manufacturing	90	Not reported	(i) Mean percent FEV1 predicted: 76.9% (exposed) and 87.4% (controls), P < 0.001; (ii) mean percent FVC predicted: 77.2% (exposed) and 86.1% (controls), P < 0.001; (iii) mean FEV1/FVC percentage: 74.2% (exposed) and 82.8% (controls), P < 0.001; (iv) negative correlation between blood styrene concentration and FEV1/FVC, r = −0.49, P < 0.05 and MEF25–75%, r = −0.76, P < 0.001	++
McCague et al. [2015]	Wind energy	355	Chest tightness, cough, shortness of breath, wheezing	(i) Shortness of breath and usual cough less common, and wheezing more common than expected from adjusted comparisons with U.S. adult population; (ii) chest tightness by median current styrene exposure (mg/g creatinine): 5.0% with <53.6, 13.0% with ≥53.6, P ≤ 0.05; (iii) increased cumulative styrene exposure associated with decreased percent predicted MMEF, effect estimate = −0.026, P = 0.011; (iv) 3.5% decrease in FEV1/FVC (P < 0.05) and 5.5% decrease in FeNO (P < 0.05) with cumulative styrene exposure change from 2.5th to 97.5th percentile	++
No Association
Axelson and Gustavson [1978]	Glass fiber reinforced products manufacturing	17	Not reported	(i) 11 workers with exposure to 8 hrTWA <150 ppm (before work/after work): mean FVC, 103%/101 % of predicted; mean FEV1/FVC, 107%/106% of predicted; (ii) 6 workers with exposure to 8 hTWA >150 ppm (before work/after work): mean FVC, 101 %/101% of predicted; mean FEV1/FVC, 103%/102% of predicted	NA
Thiess and Friedheim [1978]	Styrene manufacturing	177	Bronchial asthma, chronic bronchitis	(i) Air concentrations generally <1 ppm, occasionally up to 8 ppm, highest excursion was 47 ppm; (ii) urine mandelic acid <50 mg/L in 61 (91%) of 67 styrene or polystyrene workers; (iii) 6 (7%) of 84 styrene workers had chronic bronchitis; 8 (9%) of 93 polystyrene workers had bronchial asthma	NA

CDC, Centers for Disease Control and Prevention; CXR, chest X-ray; FeNO, fraction of exhaled nitric oxide; FEV₁, forced expiratory volume in 1s; FVC, forced vital capacity; h, hour; LOD, limit of detection; MEF, mid-expiratory flow; MMEF, maximal mid-expiratory flow; NA, no association; NS, non-significant (P ≥ 0.05); OB, obliterative bronchiolitis; OR, odds ratio; PEF, peak expiratory flow; ppm, parts per million; RR, relative risk; TWA, time-weighted average

^aStrength of evidence for positive association: +++, strong; ++, intermediate; +, suggestive; NA, no association; see Table I for definitions.

^bPresence of urinary mandelic acid indicates metabolism of styrene.