Carbon Tetrachloride Epidemiology and Liver Toxicity

Chemical-Specific Epidemiology Summary

Carbon Tetrachloride (CASRN 56-23-5)

RoseyFields evaluates the human epidemiological evidence for carbon tetrachloride as follows. This summary catalogs the populations, exposure metrics, and health outcomes examined in the published epidemiological literature, characterizes the strength and consistency of the evidence for each outcome, and describes how RoseyFields integrates this evidence with the toxicological dose-response record (described in RoseyFields’ companion Risk Assessment Methodology document) to support causation opinions in litigation and regulatory matters.

1. Overview of Study Populations and Data Sources

The epidemiological record for carbon tetrachloride spans several distinct population types, each contributing a different strength to the overall weight of evidence, and each subject to a different pattern of limitation.

1.1 Occupational Cohorts

The largest body of quantitative evidence comes from retrospective occupational cohort mortality studies. These include a cohort of 1,919 men employed for one or more years (1940–1969) at a chemical manufacturing facility that produced chlorinated methanes, including carbon tetrachloride (Thun et al., 1985, addressing the related chlorinated-methane-worker cohort discussed further in RoseyFields’ cadmium and cross-chemical files; for carbon tetrachloride specifically, see the chlorinated-solvent cohorts below); a cohort of 330 laundry and dry cleaning workers potentially exposed to carbon tetrachloride, trichloroethylene, and tetrachloroethylene (Blair et al., 1979); an expanded cohort of dry cleaners (Blair et al., 1990); and a very large cohort of 14,457 aircraft maintenance workers at a U.S. Air Force facility, of whom 6,737 had documented exposure to carbon tetrachloride, studied with an extensive job-exposure matrix (Stewart et al., 1991; Blair et al., 1998) and followed further in Radican et al. (2008).

1.2 Population-Based Case-Control Studies

A second body of evidence comes from population-based case-control studies that assessed carbon tetrachloride as one of many occupational exposures evaluated against specific cancer outcomes, typically using detailed job-exposure matrices or expert industrial-hygiene review rather than biomonitoring. These include a large Montreal-area case-control study of workplace substances and multiple cancer sites (Siemiatycki, 1991); a cross-Canada case-control study of non-Hodgkin lymphoma (NHL) and pesticide/solvent exposures (McDuffie et al., 2001); a Connecticut case-control study of NHL in women (Wang et al., 2009); a cohort of Finnish laboratory workers evaluated for cancer incidence in relation to chemical carcinogen exposure, including carbon tetrachloride (Kauppinen et al., 2003); a case-control study of female breast cancer mortality and occupational solvent exposure (Cantor et al., 1995); a case-control study of astrocytic brain cancer (Heineman et al., 1994); and a hypothesis-generating case-control study of rectal cancer and occupational exposures (Dumas et al., 2000).

1.3 Cross-Sectional Clinical/Biomonitoring Studies

A third body of evidence comes from cross-sectional occupational health surveillance studies that directly measured clinical and biochemical indicators of target-organ function in currently exposed workers, most notably a study of hepatic and hematologic function in 135 carbon-tetrachloride-exposed workers and 276 non-exposed controls across three industrial sites, with exposure quantified using historical personal air-monitoring data by job category (Tomenson et al., 1995).

1.4 Community/Environmental Exposure and Birth-Outcome Studies

A fourth body of evidence addresses non-occupational, environmental exposure — principally, contamination of public drinking-water supplies — and its relationship to birth outcomes, using a combination of cross-sectional and case-control designs in populations near contaminated water systems in New Jersey (Bove et al., 1995).

1.5 Case Reports and Case Series

Finally, a substantial body of clinical case-report and case-series literature documents acute, high-level poisoning events (occupational, accidental, or intentional), providing detailed clinical and, in some instances, histopathological description of acute hepatic, renal, and pulmonary effects, and several case reports of liver tumors arising after documented heavy carbon tetrachloride exposure (Docherty and Burgess, 1922; Docherty and Nicholls, 1923; Norwood et al., 1950; Stewart et al., 1963; New et al., 1962; Kazantzis and Bomford, 1960; Ruprah et al., 1985; Johnstone, 1948; Simler et al., 1964; Tracy and Sherlock, 1968).

1.6 Value of Using Multiple, Diverse Populations

RoseyFields’ methodology places particular weight on the fact that these five population types differ systematically in their sources of bias. Occupational cohorts are subject to the healthy-worker effect and, in older cohorts, to substantial co-exposure to other chlorinated solvents, but provide large sample sizes and long follow-up. Case-control studies with job-exposure-matrix-based assessment reduce reliance on a single employer’s records and allow examination of rarer outcomes, but are vulnerable to recall bias and exposure misclassification. Cross-sectional clinical studies provide direct, quantitative, dose-related biomarker data but cannot address latent outcomes such as cancer. Community/drinking-water studies capture non-occupational, lower-level, chronic exposure relevant to environmental contamination litigation, but typically have cruder exposure characterization than occupational studies. Case reports, while not capable of establishing causation on their own, provide clinical detail on acute mechanisms of injury (e.g., time course of hepatic and renal failure) that is difficult to obtain from any cohort design. Because each design’s principal weaknesses differ, a consistent finding that recurs across several of these designs and populations — as is seen for acute hepatotoxicity, and to a lesser degree for non-Hodgkin lymphoma risk — carries materially more weight under a Bradford Hill-type causal framework than any single well-conducted study standing alone; conversely, an isolated finding present in only one design (for example, breast or brain cancer associations reported in single case-control analyses) warrants more caution.

2. Health Outcomes Investigated in Humans, by Body System

The following organizes all outcomes RoseyFields has identified in the peer-reviewed human literature, grouped by body system, and classified into three evidentiary tiers: (A) strong, consistent, quantitatively modeled evidence; (B) suggestive but inconsistent evidence; and (C) outcomes investigated with null or inadequate findings.

2.1 Hepatic (Liver) System

Tier A — Strong, Consistent Evidence: Acute Hepatocellular Injury

Acute, high-level carbon tetrachloride exposure (occupational, accidental, or intentional) is consistently and repeatedly associated with hepatocellular injury in humans, evidenced by elevated serum transaminases (AST/ALT), jaundice, hepatomegaly, and, in fatal cases, centrilobular hepatic necrosis on autopsy. This pattern recurs across multiple independent case series spanning nearly a century, from early autopsy reports (Docherty and Burgess, 1922; Docherty and Nicholls, 1923) through mid-century industrial poisoning reports (Norwood et al., 1950; Stewart et al., 1963) to a 19-patient clinical case series with detailed biochemical follow-up (Ruprah et al., 1985). The consistency of this finding across time, geography, and clinical setting, together with the biological plausibility established by the animal dose-response literature (see RoseyFields’ companion methodology document), places acute hepatotoxicity in the highest-confidence tier.

Tier B — Suggestive but Inconsistent Evidence: Subclinical/Chronic Hepatic Effects at Low-Level Occupational Exposure

At lower, chronic occupational exposure levels, the evidence is considerably weaker and inconsistent. Tomenson et al. (1995) found statistically significant elevations in alkaline phosphatase and gamma-glutamyl transferase in workers with medium exposure (1.1–3.9 ppm time-weighted average) relative to controls, but values in the highest exposure category (≥4.0 ppm) did not differ significantly from controls, no exposure-response gradient was observed across the full range, and a clinical review of exposed workers with abnormal results did not identify clinically evident liver disease attributable to exposure. A follow-up survey three years later at the highest-exposure site found no further change in liver function indices. RoseyFields characterizes this as suggestive, not confirmatory, evidence of subclinical hepatic effects at chronic, moderate occupational exposure levels.

Tier A/limited — Liver Cancer: Case Reports Only, No Cohort Confirmation

Three individual case reports describe primary liver cancer arising in patients with a documented history of heavy carbon tetrachloride exposure and pre-existing cirrhosis (Johnstone, 1948; Simler et al., 1964; Tracy and Sherlock, 1968). These reports are informative as to biological plausibility (they parallel the rodent hepatocarcinogenicity findings) but, as uncontrolled case reports in patients with a confounding pre-existing liver disease, cannot support a quantitative or even qualitative cohort-level causal inference. No occupational cohort mortality study identified in this review has reported a statistically significant excess of liver cancer specifically attributable to carbon tetrachloride exposure; this outcome is therefore properly classified as Tier C (inadequate cohort evidence) notwithstanding the qualitative case-report signal, a distinction RoseyFields’ methodology treats as important.

2.2 Renal (Kidney) System

Tier A — Strong, Consistent Evidence: Acute Renal Injury Following Acute Poisoning

Acute renal failure, typically delayed in onset relative to hepatic injury, is a well-documented consequence of acute, high-level carbon tetrachloride poisoning, described consistently across multiple independent case reports and series (New et al., 1962; Stewart et al., 1963; Ruprah et al., 1985). Secondary pulmonary effects (e.g., pulmonary edema) attributable to renal failure following acute poisoning have also been documented (Umiker and Pearce, 1953).

Tier C — Chronic Occupational Renal Effects

No consistent evidence of chronic renal impairment has been demonstrated at chronic, low-to-moderate occupational exposure levels; the Tomenson et al. (1995) cross-sectional study, which included renal indices among the broader biochemical panel, did not identify a dose-related pattern of chronic renal dysfunction distinguishable from the hepatic signal described above.

2.3 Hematologic/Lymphatic and Lymphohematopoietic Malignancy

Tier B — Suggestive but Inconsistent Evidence: Non-Hodgkin Lymphoma and Related Malignancies

Non-Hodgkin lymphoma (NHL) is the outcome for which the epidemiological signal — while still inconsistent — is most frequently reported across independent occupational and case-control studies. In the extended follow-up of the aircraft-maintenance-worker cohort, carbon tetrachloride exposure was associated with an elevated relative risk of NHL in women (RR 3.3; 95% CI 0.9–12.7; 8 exposed cases) and a smaller, non-significant elevation in men (RR 1.2; 95% CI 0.4–3.3; 14 exposed cases), alongside an elevated risk of multiple myeloma in women (RR 2.0; 95% CI 0.4–9.1) (Blair et al., 1998); a subsequent extended follow-up of the same cohort (Radican et al., 2008) found the NHL risk estimate attenuated relative to the earlier analysis, though still nonsignificantly elevated. A cross-Canada case-control study found a statistically significant association between carbon tetrachloride exposure (via pesticide-related use) and NHL risk in men (McDuffie et al., 2001). A Connecticut population-based case-control study similarly reported a statistically significant association between occupational carbon tetrachloride exposure and NHL risk in women (Wang et al., 2009). A cohort of Finnish laboratory workers found a small, statistically nonsignificant excess of NHL among those with potential carbon tetrachloride exposure (Kauppinen et al., 2003). By contrast, the Montreal case-control study found no elevated NHL risk associated with carbon tetrachloride exposure (odds ratio 0.4; 90% CI 0.1–2.5, based on only 3 exposed cases) (Siemiatycki, 1991), and a cohort of chlorinated-methane production workers examined for leukemia and lymphosarcoma risk did not find a clear, consistent excess attributable specifically to carbon tetrachloride as distinct from co-exposures (Checkoway et al., 1984; Wilcosky et al., 1984).

RoseyFields characterizes the overall NHL signal as suggestive but inconsistent: several independent studies, using different populations and exposure assessment methods, report point estimates above unity, and two report statistical significance, but confidence intervals are wide (reflecting small numbers of exposed cases in nearly every study), one well-designed case-control study found no association, and no study has fully isolated carbon tetrachloride from co-exposure to other chlorinated solvents historically used in the same occupational settings (e.g., trichloroethylene, tetrachloroethylene). Lymphocytic leukemia and multiple myeloma show a similar, weaker version of this same suggestive-but-inconsistent pattern (Checkoway et al., 1984; Wilcosky et al., 1984; Blair et al., 1998).

2.4 Other Malignancies

Tier C — Null or Inadequate Evidence

A number of other cancer sites have been examined in one or two studies each, generally without a consistent or statistically significant association, and in most cases without replication in an independent population: esophageal and cervical cancer among dry cleaning workers (Blair et al., 1979, 1990) — findings potentially confounded by tetrachloroethylene co-exposure and, for cervical cancer, by non-occupational risk factors; breast cancer mortality in relation to occupational solvent exposure (Cantor et al., 1995); astrocytic brain cancer (Heineman et al., 1994); rectal cancer, in a hypothesis-generating analysis explicitly described by its own authors as preliminary (Dumas et al., 2000); and, in the Montreal case-control study, esophagus, stomach, colon, pancreas, prostate, kidney, and skin melanoma, none of which showed an excess associated with carbon tetrachloride exposure (Siemiatycki, 1991). RoseyFields classifies all of these outcomes as Tier C: the available data are inadequate — whether because of a single-study result, small numbers, or unaddressed confounding by co-exposures — to support even a suggestive causal inference.

Liver cancer, notwithstanding the case reports discussed in Section 2.1, is likewise properly classified as Tier C at the cohort/case-control level: no cohort mortality study has demonstrated a statistically significant excess of liver cancer specifically attributable to carbon tetrachloride, a point emphasized in independent expert reviews of this literature (see Section 6, discussing Cohen et al., 2023).

2.5 Reproductive and Developmental Outcomes

Tier B — Suggestive but Inconsistent Evidence

A New Jersey population-based study examined maternal residence in areas with drinking-water contamination (including carbon tetrachloride, among other volatile organic compounds) and adverse birth outcomes, finding the strongest association with low term birth weight (Bove et al., 1995). Because affected water systems were contaminated with multiple co-occurring volatile organic compounds and the exposure assessment could not isolate carbon tetrachloride from other constituents, and because no comparably designed replication study specific to carbon tetrachloride alone has been published, RoseyFields classifies this finding as suggestive rather than confirmatory of a chemical-specific developmental effect.

2.6 Central Nervous System and Constitutional Symptoms

Tier A — Strong, Consistent Evidence: Acute CNS Depression

Headache, dizziness, and generalized weakness consistent with acute central nervous system depression are consistently reported across essentially every acute clinical poisoning case series identified (Stewart et al., 1963; Ruprah et al., 1985; Kazantzis and Bomford, 1960), alongside acute gastrointestinal symptoms (nausea, vomiting, abdominal pain). This pattern is highly consistent across decades of case reports and is not seriously disputed.

Tier C — Chronic Neurobehavioral Effects

Chronic, low-level occupational exposure has not been systematically evaluated for subclinical neurobehavioral effects in a dedicated cohort study identified in this review, and RoseyFields treats this as an evidence gap rather than a null finding.

2.7 Hematological Parameters

Tier C — Null or Inadequate Evidence

Clinically significant hematological effects (e.g., marrow suppression) are not typically observed following inhalation exposure in the occupational literature (Norwood et al., 1950); the Tomenson et al. (1995) cross-sectional study found small (2.5–3.6%) statistically significant reductions in some hematological indices (hemoglobin, packed cell volume, red cell count) without a consistent dose-response gradient, and the study investigators concluded these differences were not attributable to carbon tetrachloride exposure. Isolated case reports of mild-to-severe anemia following poisoning exist but are not systematically replicated.

3. Summary Table of Evidence Tiers

4. Detailed Review of Strong-Evidence Outcomes

4.1 Acute Hepatocellular and Renal Injury

Exposure Metrics: These studies rely on documented acute occupational, accidental, or intentional exposure events, typically vapor inhalation in an enclosed or poorly ventilated space, with exposure intensity inferred from clinical severity, occupational history, and (where available) air-monitoring or product-use records, rather than from serum or breath biomonitoring of carbon tetrachloride itself. Effect Sizes/Direction: Findings are qualitative and clinical rather than expressed as relative risks — e.g., serum transaminase elevations of severalfold to several-hundred-fold above normal, progressive azotemia, and, in fatal cases, histologically confirmed centrilobular hepatic necrosis (Ruprah et al., 1985; Stewart et al., 1963). Consistency: This pattern — early hepatic injury (24–48 hours) followed by delayed renal injury (2–7 days) — recurs with striking consistency across case series separated by 40+ years and multiple countries (Docherty & Burgess, 1922, in the United Kingdom; Norwood et al., 1950 and New et al., 1962, in the United States; Ruprah et al., 1985, in the United Kingdom), a temporal and geographic consistency that strongly supports a direct causal relationship for this acute, high-dose outcome — a conclusion that is not seriously disputed in the toxicological or medical literature.

4.2 Non-Hodgkin Lymphoma

Exposure Metrics: Exposure assessment across the NHL literature is heterogeneous. The aircraft-maintenance-worker studies (Blair et al., 1998; Radican et al., 2008) used a detailed, chemical-specific job-exposure matrix built from historical personnel and industrial-hygiene records (Stewart et al., 1991), permitting semi-quantitative categorization of cumulative exposure. The case-control studies (McDuffie et al., 2001; Wang et al., 2009) relied on self-reported occupational history combined with expert or algorithmic exposure assignment, an inherently less precise method. The Finnish laboratory-worker study (Kauppinen et al., 2003) used a national job-exposure matrix (FINJEM) rather than individual monitoring data. Effect Sizes/Direction: As detailed in Section 2.3, point estimates across these studies are generally elevated (RR/OR in the range of roughly 1.2 to 3.3), with the higher and statistically significant estimates concentrated in women (Blair et al., 1998; Wang et al., 2009) and in the pesticide-applicator-focused Cross-Canada study (McDuffie et al., 2001). Consistency: The direction of effect (RR/OR > 1) is consistent across most, though not all, studies, but confidence intervals are wide in every study (reflecting small numbers of carbon-tetrachloride-exposed NHL cases even in these large cohorts), and the one large, well-designed population-based case-control study with a broad occupational exposure matrix (Siemiatycki, 1991) found no elevated risk. RoseyFields’ assessment is that this body of evidence supports a suggestive, not established, association, consistent with the classification adopted in several independent reviews of this literature (see Section 6).

4.3 Subclinical Hepatic Enzyme Changes at Chronic Occupational Exposure

Exposure Metrics: Tomenson et al. (1995) is distinguished within this literature by its use of quantitative, job-category-specific historical personal air-monitoring data to stratify 135 exposed workers into low (≤1 ppm), medium (1.1–3.9 ppm), and high (≥4.0–11.9 ppm) time-weighted-average exposure categories, compared against 276 non-exposed controls, with alcohol consumption (a major hepatic confounder) collected and found equivalent across groups. Effect Sizes/Direction: Alkaline phosphatase and gamma-glutamyl transferase were statistically significantly elevated in the medium-exposure group relative to controls, but not in the high-exposure group, and duration of employment showed no significant effect on enzyme levels. Consistency: The absence of a monotonic exposure-response relationship (elevated at medium but not high exposure) is a notable internal inconsistency that limits confidence in a causal interpretation of this finding, and a three-year follow-up survey at the highest-exposure site found no progression of any liver-function abnormality, further weakening the case for a chronic, exposure-related hepatic effect at these exposure levels — in contrast to the strong, dose-independent signal seen for acute high-dose poisoning.

5. Study Quality Considerations

RoseyFields’ confidence in any individual epidemiological finding is calibrated against the following recurring quality considerations in the carbon tetrachloride literature:

5.1 Co-Exposure to Other Chlorinated Solvents

Nearly every occupational cohort and case-control study identified involved workers with concurrent or historical exposure to other chlorinated solvents — most commonly trichloroethylene and tetrachloroethylene — used interchangeably or sequentially for degreasing and dry-cleaning applications (Blair et al., 1979, 1990, 1998; Checkoway et al., 1984; Wilcosky et al., 1984). Because these co-exposed solvents have their own, independently documented associations with several of the same outcomes (notably NHL, kidney, and liver/biliary cancers), few if any studies can fully isolate a carbon-tetrachloride-specific effect from a solvent-class effect. This is the single most important limitation on the specificity of the cancer findings summarized in Section 2, and RoseyFields flags it explicitly whenever an NHL or other cancer finding is used to support a causation opinion.

5.2 Exposure Misclassification

With the partial exception of the aircraft-maintenance-worker cohort (which benefited from an unusually detailed, chemical-specific job-exposure matrix; Stewart et al., 1991) and the Tomenson et al. (1995) cross-sectional study (which used historical personal air monitoring), most epidemiological studies of carbon tetrachloride rely on job-title-based or self-reported exposure classification, without direct biomonitoring of serum, breath, or urine carbon tetrachloride or its metabolites. This non-differential misclassification, where present, would generally be expected to bias relative-risk estimates toward the null, meaning that some true associations may be underestimated — but differential misclassification (e.g., in case-control studies relying on recall after cancer diagnosis) cannot be ruled out and could bias estimates in either direction.

5.3 Confounding

Beyond co-exposure to other solvents, alcohol consumption is a well-recognized confounder for hepatic outcomes specifically, and was appropriately measured and found balanced across exposure groups in the best-designed cross-sectional study (Tomenson et al., 1995), but was not systematically addressed in most cohort mortality studies. Smoking is a recognized confounder for several malignancies examined (e.g., esophageal cancer in the dry-cleaner cohorts; Blair et al., 1979, 1990) and was inconsistently controlled for across the literature. Socioeconomic and lifestyle factors are potential residual confounders in the community drinking-water study of birth outcomes (Bove et al., 1995), which could not fully adjust for these factors given its ecological/semi-ecological design.

5.4 Reverse Causation and the Healthy-Worker Effect

Occupational cohort mortality studies are subject to the healthy-worker effect (workers are, on average, healthier than the general population used as the referent), which tends to bias overall mortality ratios toward the null or below unity and could mask a true excess risk; RoseyFields considers this when interpreting non-significant or modestly elevated standardized mortality ratios in these cohorts as potentially understating, rather than overstating, an underlying association. Reverse causation is not a material concern for the acute poisoning case-series literature (Section 4.1), given the immediate, well-documented temporal relationship between exposure and onset of injury, but is a more relevant consideration for the chronic, low-level occupational and community exposure literature, where subclinical disease could in principle influence exposure duration or job assignment (e.g., through voluranteer/self-selection out of higher-exposure jobs).

5.5 Small Numbers of Exposed Cases

A recurring statistical limitation across the case-control literature on NHL and other rare cancers is a small absolute number of carbon-tetrachloride-exposed cases (frequently fewer than 15 exposed cases per study), which produces wide confidence intervals and limited statistical power to detect or rule out a moderate true effect (Blair et al., 1998; McDuffie et al., 2001; Wang et al., 2009; Kauppinen et al., 2003). RoseyFields treats a wide confidence interval crossing unity as materially different from — and a weaker basis for causal inference than — a precise null finding from a well-powered study.

6. Independent Expert Panel and Agency Weight-of-Evidence Conclusions

The International Agency for Research on Cancer (IARC) evaluated carbon tetrachloride and classified it in Group 2B (possibly carcinogenic to humans), concluding that the epidemiological evidence in humans is inadequate to establish carcinogenicity, while noting the suggestive, but not conclusive, pattern of association with NHL and related lymphohematopoietic malignancies described in Section 2.3, and the sufficient evidence of carcinogenicity in experimental animals (IARC, 1999). The U.S. National Toxicology Program’s Report on Carcinogens similarly classifies carbon tetrachloride as reasonably anticipated to be a human carcinogen, a determination that — consistent with RoseyFields’ own tiered classification above — rests principally on the animal bioassay data together with the suggestive human lymphohematopoietic-malignancy signal, and explicitly notes that epidemiological data are inadequate to directly evaluate a human liver-cancer association.

An independent expert critique of the full carbon tetrachloride carcinogenicity data package (Cohen et al., 2023) likewise concluded that the available human epidemiological studies do not provide credible evidence of an increased risk of liver or adrenal-gland cancer specifically, and identified serious methodological limitations (principally, co-exposure confounding and small numbers) that limit the usefulness of the existing human cancer studies for quantitative risk assessment — a conclusion consistent with RoseyFields’ Tier C classification of liver cancer at the cohort level in Section 2.1, notwithstanding the qualitative case-report signal. RoseyFields’ own weight-of-evidence approach, summarized in the tiered table in Section 3, is consistent with — and independently derived from the same primary literature as — these agency and expert-panel determinations.

7. Use of Epidemiological Evidence to Support Causation Opinions

7.1 General Causation

RoseyFields’ general causation opinions integrate the epidemiological tiering in Section 3 with the animal toxicology and dose-response record described in the companion Risk Assessment Methodology document. For Tier A outcomes (acute hepatic and renal injury, acute CNS depression), the human evidence alone — independent of the animal data — is sufficient to support general causation for acute, high-level exposure scenarios, given the consistency, temporal relationship, and biological plausibility of the finding across an extensive case-report literature spanning many decades and countries. For Tier B outcomes (most significantly, NHL and related lymphohematopoietic malignancies, and low birth weight associated with drinking-water contamination), RoseyFields’ opinion is that the human evidence, standing alone, is suggestive but not independently sufficient to establish general causation; in these instances, RoseyFields’ opinion relies on the human evidence in combination with the animal carcinogenicity data (adrenal pheochromocytoma and hepatocellular tumor induction; see companion methodology document) and the biological plausibility of an immune/hematopoietic or reproductive effect, while candidly noting the co-exposure confounding and small-numbers limitations described in Section 5. For Tier C outcomes (liver cancer at the cohort level, most other solid-tumor associations, chronic renal and hematological effects), RoseyFields does not offer an opinion that the epidemiological evidence, standing alone or together with the animal data, establishes general causation, though RoseyFields notes that animal data may independently support a hazard concern for some of these outcomes (e.g., liver cancer) that is not confirmed, but also not ruled out, by the inadequate human data.

7.2 Specific Causation

For specific causation opinions in individual litigation matters, RoseyFields’ epidemiologists and toxicologists layer the general-causation framework above against case-specific facts: documented or reconstructed exposure intensity and duration (see the exposure/dose reconstruction methodology in the companion document), the specific health outcome(s) alleged, latency between first exposure and diagnosis (particularly relevant for the Tier B malignancy outcomes, where induction-latency periods of a decade or more are biologically expected), the presence of alternative or competing causes and co-exposures (alcohol use, smoking, other solvent exposure, hepatitis or other pre-existing hepatic disease, family/genetic cancer history), and, where available, differential diagnosis excluding other established causes of the alleged condition. RoseyFields’ opinions distinguish explicitly between the population-level, probabilistic nature of the epidemiological evidence (which speaks to whether carbon tetrachloride can cause a given outcome, and at what population-attributable magnitude) and the individualized clinical and exposure facts necessary to opine that it did cause a given outcome in a specific individual, consistent with generally accepted principles of epidemiological and toxicological causation analysis in environmental and toxic tort litigation.

8. Bibliography

(Author-year citations above correspond to the following peer-reviewed epidemiological sources and independent expert/agency determinations, listed alphabetically.)

Blair, A; Decoufle, P; Grauman, D. (1979) Causes of death among laundry and dry cleaning workers. Am J Public Health 69:508–511.

Blair, A; Stewart, PA; Tolbert, PE. (1990) Cancer and other causes of death among a cohort of dry cleaners. Br J Ind Med 47:162–168.

Blair, A; Hartge, P; Stewart, PA; et al. (1998) Mortality and cancer incidence of aircraft maintenance workers exposed to trichloroethylene and other organic solvents and chemicals: extended follow-up. Occup Environ Med 55:161–171.

Bove, FJ; Fulcomer, MC; Klotz, JB; et al. (1995) Public drinking water contamination and birth outcomes. Am J Epidemiol 141:850–862.

Cantor, KP; Stewart, PA; Brinton, LA; et al. (1995) Occupational exposures and female breast cancer mortality in the United States. J Occup Environ Med 37:336–348.

Checkoway, H; Wilcosky, T; Wolf, P; et al. (1984) An evaluation of the associations of leukemia and rubber industry solvent exposures. Am J Ind Med 5:239–249.

Cohen, SM; Bevan, C; Gollapudi, B; Klaunig, JE. (2023) Evaluation of the carcinogenicity of carbon tetrachloride. J Toxicol Environ Health B Crit Rev 26:311–338.

Docherty, JF; Burgess, E. (1922) The action of carbon tetrachloride on the liver. Br Med J 2:907–908.

Docherty, JF; Nicholls, L. (1923) Report of three autopsies following carbon tetrachloride treatment. Br Med J 2:753.

Dumas, S; Parent, ME; Siemiatycki, J; et al. (2000) Rectal cancer and occupational risk factors: a hypothesis-generating, exposure-based case-control study. Int J Cancer 87:874–879.

Heineman, EF; Cocco, P; Gomez, MR; et al. (1994) Occupational exposure to chlorinated aliphatic hydrocarbons and risk of astrocytic brain cancer. Am J Ind Med 26:155–169.

IARC (International Agency for Research on Cancer). (1999) Carbon tetrachloride. In: Re-evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 71. Lyon, France: IARC, pp. 401–432.

Johnstone, RT. (1948) Carbon tetrachloride poisoning and primary carcinoma of the liver. J Ind Hyg Toxicol 30:20–22.

Kauppinen, T; Pukkala, E; Saalo, A; Sasco, AJ. (2003) Exposure to chemical carcinogens and risk of cancer among Finnish laboratory workers. Am J Ind Med 44:343–350.

Kazantzis, G; Bomford, RR. (1960) Dyspepsia due to inhalation of carbon tetrachloride vapor. Lancet 1:360–362.

McDuffie, HH; Pahwa, P; McLaughlin, JR; et al. (2001) Non-Hodgkin’s lymphoma and specific pesticide exposures in men: cross-Canada study of pesticides and health. Cancer Epidemiol Biomarkers Prev 10:1155–1163.

New, PS; Lubash, GD; Scherr, L; et al. (1962) Acute renal failure associated with carbon tetrachloride intoxication. J Am Med Assoc 181:903–906.

Norwood, WD; Fuqua, PA; Scudder, BC. (1950) Carbon tetrachloride poisoning. Arch Ind Hyg Occup Med 1:90–100.

NTP (National Toxicology Program). Report on Carcinogens, Fifteenth Edition — Carbon Tetrachloride. Research Triangle Park, NC.

Radican, L; Blair, A; Stewart, P; Wartenberg, D. (2008) Mortality of aircraft maintenance workers exposed to trichloroethylene and other hydrocarbons and chemicals: extended follow-up. J Occup Environ Med 50:1306–1319.

Ruprah, M; Mant, TGK; Flanagan, RJ. (1985) Acute carbon tetrachloride poisoning in 19 patients: implications for diagnosis and treatment. Lancet 1:1027–1029.

Siemiatycki, J, ed. (1991) Risk Factors for Cancer in the Workplace. Boca Raton, FL: CRC Press.

Simler, M; Maurer, G; Mandard, JC. (1964) [Cirrhosis and primary cancer of the liver caused by carbon tetrachloride]. Arch Mal Prof 25:305–308.

Stewart, RD; Boettner, EA; Southworth, RR; et al. (1963) Acute carbon tetrachloride intoxication. J Am Med Assoc 183:94–97.

Stewart, PA; Lee, JS; Marano, DE; et al. (1991) Retrospective cohort mortality study of workers at an aircraft maintenance facility. II. Exposures and their assessment. Br J Ind Med 48:531–537.

Tomenson, JA; Baron, CE; O’Sullivan, JJ; et al. (1995) Hepatic function in workers occupationally exposed to carbon tetrachloride. Occup Environ Med 52:508–514.

Tracy, GD; Sherlock, S. (1968) Primary carcinoma of the liver following carbon tetrachloride poisoning. Med J Aust 1:11–13.

Umiker, W; Pearce, J. (1953) Nature and genesis of pulmonary alterations in carbon tetrachloride poisoning. Arch Pathol 55:203–217.

Wang, R; Zhang, Y; Lan, Q; et al. (2009) Occupational exposure to solvents and risk of non-Hodgkin lymphoma in Connecticut women. Am J Epidemiol 169:176–185.

Wilcosky, TC; Checkoway, H; Marshall, EG; Tyroler, HA. (1984) Cancer mortality and solvent exposures in the rubber industry. Am Ind Hyg Assoc J 45:809–811.

This epidemiology summary is prepared by RoseyFields for internal and client reference and reflects the peer-reviewed human epidemiological literature on carbon tetrachloride as summarized above. Application to any specific individual or matter requires additional case-specific exposure reconstruction and medical/differential-diagnosis review, and is documented separately.