title: Early effects of low benzene exposure on blood cell counts in Bulgarian petrochemical workers.
abstract: OBJECTIVE
  Only few studies have examined early hematological effects in human populations exposed to low benzene levels and their findings are controversial. We evaluated hematological outcomes (WBC, neutrophils, lymphocytes, monocytes, eosinophils, basophils, RBC, Hb, HCT MCV, platelets and MPV) in a population of 153 Bulgarian petrochemical workers exposed to benzene (range 0.01-23.9 ppm) and 50 unexposed subjects.
  
  
  METHODS
  Written informed consent was obtained and a self-administered questionnaire used to collect information on current smoking habits, lifestyle, and occupational activities. Exposure assessment was based on personal monitoring sampling the day before phlebotomy. Urinary trans-trans-muconic acid (t,t-MA) was determined at the beginning and end of the work shift. Based on individual airborne benzene measurements, study subjects were categorized in three exposure categories (referents, <1 and > or =1 ppm). Mean values of each hematologic outcomes in each exposure category were compared with the referent group using a multiple linear regression model adjusted for age, gender, current smoking habits and environmental toluene level. The influence of the CYP2E1 (RsaI and DraI) and NQO1 609C>T genetic polymorphisms on differential hematological parameters was also investigated.
  
  
  RESULTS
  No dose-response effect was observed for most of the examined hematological outcomes (WBC, lymphocytes, neutrophils, monocytes, RBC, Hb, HCT, MCV, platelets and MPV). The eosinophil count was inversely related to benzene exposure only among smokers. Conversely, basophils increased with increasing exposure. No effect on benzene hematotoxicity was found for any of the investigated polymorphisms.
  
  
  CONCLUSIONS
  In our study we did not find a decline in WBC and lymphocytes related to benzene exposure. A myeloproliferative effect of benzene is highly unlikely to explain the observed reduction in eosinophils and increase in basophils as it would lead to a concordant depression in all granulocyte subpopulations. Whether benzene effects at low doses are present in Caucasian populations remains uncertain, thus warranting further investigations.
authors.affiliation: Department of Occupational and Environmental Health, Clinica del Lavoro L. Devoto, University of Milan, Italy.
authors.forename: Angela Cecilia
authors.initials: AC
authors.lastname: Pesatori
authors.forename: S
authors.initials: S
authors.lastname: Garte
authors.forename: T
authors.initials: T
authors.lastname: Popov
authors.forename: Tzveta
authors.initials: T
authors.lastname: Georgieva
authors.forename: T
authors.initials: T
authors.lastname: Panev
authors.forename: M
authors.initials: M
authors.lastname: Bonzini
authors.forename: D
authors.initials: D
authors.lastname: Consonni
authors.forename: M
authors.initials: M
authors.lastname: Carugno
authors.forename: B D
authors.initials: BD
authors.lastname: Goldstein
authors.forename: Emanuela
authors.initials: E
authors.lastname: Taioli
authors.forename: V
authors.initials: V
authors.lastname: Fontana
authors.forename: Elena
authors.initials: E
authors.lastname: Stagi
authors.forename: P A
authors.initials: PA
authors.lastname: Bertazzi
authors.forename: D F
authors.initials: DF
authors.lastname: Merlo
mesh_terms: D000328:Adult; D001554:Benzene / Q000009:adverse effects*; D001772:Blood Cell Count; D002031:Bulgaria; D002617:Chemical Industry; D005260:Female; D006801:Humans; D008297:Male; D016273:Occupational Exposure / Q000009:adverse effects*; D010578:Petroleum; D013997:Time Factors
chemical_list: D010578:Petroleum; D001554:Benzene