Biomedical subjects

T H Milby

Publications and source records attributed to T H Milby.

At least 19 recordsLinked to original sources

PubMed1999

Hydrogen sulfide poisoning: clarification of some controversial issues.

BACKGROUND: Hydrogen sulfide is a toxic gas about which much has been written. We discuss here several issues we believe would benefit from further clarification. CONCLUSIONS: We conclude that: 1) Certain neurotoxic effects of exposure are probably due to a direct toxic effect on the brain, while others are almost certainly a result of hypoxia secondary to H2S-induced respiratory insufficiency; 2) pulmonary edema is a common consequence of poisoning and there is suggestive evidence of hyperactive airway responses in some individuals following brief H2S-induced unconsciousness (knockdown); 3) criteria for acceptable community levels are very different than those governing occupational standards; 4) urinary thiosulfate determinations can be useful for monitoring occupational exposure; and 5) determination of sulfide ion concentrations in blood or major organs can be useful in corroborating a diagnosis of fatal H2S toxicity, but there are many pitfalls in collecting, storing, and analyzing tissue and fluid samples.

Air Pollutants↗

PubMed1985

PCB-containing transformer fires: decontamination guidelines based on health considerations.

Realization that polychlorinated biphenyl-(PCB)-containing (askarel) transformer fires can produce toxic polychlorinated dibenzofuran (PCDF) and polychlorinated dibenzodioxin (PCDD) isomers has led to efforts to develop guidelines for cleanup of structures contaminated by soot from these fires. Two such fires have occurred in the United States in recent years, one in 1981 in Binghamton, N.Y., the other in 1983 in San Francisco. The phenomenon of PCB transformation to more toxic substances under conditions of uncontrolled combustion was studied in both locations, but much more extensively in New York. In terms of possible danger to human health, PCDFs comprise by far the most important PCB combustion products identified in the soot of both fires. PCDDs were not formed in sufficient quantity in either fire to constitute an important health hazard. The PCDF isomers of greatest health significance are the tetra-, penta-, and hexa- forms having all four lateral positions (2,3,7 and 8) chlorinated. Separate decontamination guidelines were established for each fire, based on different toxicity and exposure assumptions. One guideline was based on carcinogenic risk assessment of 2,3,7,8-TCDD and the other on experimental animal no-observed-effect level data for the same compound. More effort will be required to develop a generally accepted set of askarel fire decontamination guidelines.

California↗

PubMed1983

The new biology and the question of personhood: implications for abortion.

Opposition to abortion is based in part on the assumption that personhood is achieved at or shortly after fertilization of the egg. This interpretation of personhood arises from a contemporary application of the ancient doctrine of preformationism, a doctrine which holds that there is a preformed individual, in an ontological sense, within the developing entity. The assumption that the fertilized egg is unique in its capacity to develop into a human being is at least in part responsible for the opinions of those opposed to abortion. Yet, the uniqueness of the zygote in its capacity to develop into an adult organism is qualified by the discovery that development may be possible in a number of other ways. Consideration of the phenomena of cloning, parthenogenesis and chimerism can relieve moral ambiguity about abortion and may reduce opposition to that practice.

Abortion, Legal↗

PubMed1981

Testicular function among epichlorohydrin workers.

Epichlorohydrin (1,2-epoxy-3-chloropropane) (ECH) is a colourless liquid used in the production of insecticides, agricultural chemicals, epoxy resins, and many other productions. It is highly reactive and an alkylating agent suspected of possessing carcinogenic properties in man. The results of a clinical-epidemiological investigation to ascertain whether exposure to ECH may be associated with sperm count suppression among ECH production workers at two chemical plants are presented. Medical histories and physical examinations with special emphasis on the genitourinary tract were completed on each participant. Blood samples and three semen specimens were also obtained. Since no internal control group were available, the data arising from this effort were analysed for each plant (plant A, 44 men; plant B, 84 men) using a control group of 90 chemical plants workers unexposed to any agents known to be toxic to the tests who were included in previous studies. This study provides no evidence that exposure to ECH at the concentrations existing at the two plants studied is responsible for sperm count suppression.

Chemical Industry↗

PubMed1981

A method for monitoring the fertility of workers. 2. Validation of the method among workers exposed to dibromochloropropane.

A method has been developed for monitoring industrial workers and others exposed to environmental agents which may impair fertility. National birth probabilities specific for maternal birth cohort, age, parity, and race are used to derive expected fertility. Observed fertility is obtained by questionnaire. Standardized fertility ratios are computed for exposure and non-exposure periods and compared. The analytic techniques have been validated by applying the method to a group of 36 male factory employees working in an agricultural chemical division (ACD) where pesticides including the nematocide dibromochloropropane were formulated. Twelve of these employees in mid-1977 had been discovered to have severely depressed sperm counts related to occupational exposure. The standardized fertility ratio (SFR) computed from data available in mid-1977 for the period at risk from employment in the ACD (SFR = 0.75) was significantly lower than those derived for the entire not-at-risk period (SFR = 1.88) and the portion related to employment in other areas of the factory (SFR = 2.16). Similar differences also were evident from data available several years earlier, demonstrating that the surveillance technique would have been capable of detecting occupationally induced infertility among these workers in advance of the actual discovery date.

Antinematodal Agents↗

PubMed1980

Epidemiological assessment of occupationally related, chemically induced sperm count suppression.

Occupationally related, chemically induced sperm count suppression is a recently recognized problem, first brought to light in connection with the manufacture and formulation of dibromochloropropane (DBCP). The authors studied sperm count data from four occupational cohorts - two exposed to DBCP and two exposed to epichlorohydrin (ECH). In both DBCP cohorts there was a significant difference (alpha = 0.05) between sperm count distribution functions of the exposed group and of the non-exposed group. A much higher percentage of exposed men was oligospermic and the median sperm count for each exposed group was substantially lower than that for the respective non-exposed group. In the ECH cohorts there was no significant difference between sperm count data for the exposed group and for the non-exposed group. The authors concluded that exposure to DBCP, but not to ECH, was positively associated with detectable sperm count suppression. It is suggested that the key to identifying and assessing occupationally related sperm count suppression lies in the proper classification and interpretation of group sperm count data.

Chemical Industry↗

PubMed1980

Recovery of testicular function among DBCP workers.

Twenty-one men with DBCP-related sperm count suppression were re-examined one year after termination of exposure in July 1977. When examined initially, 12 of these men were azoospermic and nine oligospermic. By October 1978 the sperm count of eight of the nine oligospermic men had improved considerably, six having recovered to a normospermic state. None of the 12 azoospermic men had improved by August 1978. Eleven of the 12 men exposed for more than four years were azoospermic. Serum follicle-stimulating hormone (FSH) for these 11 men increased significantly between assessments. Four children were born to the wives of the nine oligospermic men; three of the children were normal and one had several defects. The significance of this observation cannot be interpreted in terms of DBCP exposure, since this study was not designed to examine pregnancy outcome.

Chemical Industry↗

PubMed1979

Testicular function among carbaryl-exposed exployees.

A cohort of 101 male carbaryl production workers with at least 1 yr experience in the carbaryl area was selected from employment records. Of these individuals, 47 provided satifactory semen samples for analysis; 36 of the 47 provided blood for hormone assay. There were no major age or employment-status differences between those who agreed to participate and those who did not. In the absence of sufficiently detailed industrial hygiene exposure data, a subjective exposure classification was developed. No apparent relationships were found between sperm count and exposure category or years worked in classifications based on carbaryl exposure. Also, no relationship was found between fathering children and exposure to carbaryl. When the sperm-count distribution of the carbaryl-exposed workers was compared with a distribution of sperm counts representing a nonexposed (control) population, no overall differences were observed that could be related to carbaryl exposure. There was a small excess in the number of sperm counts less than 20 million per milliliter among the carbaryl-exposed men, but the excess was not significant at alpha = 0.05.

Adult↗

PubMed1979

Testicular function in DBCP exposed pesticide workers.

In mid-1977 a number of cases of infertility among male pesticide workers in California came to light. A description of this problem was published as a Preliminary Communication in The Lancet. A larger clinical-epidemiological study was undertaken to better understand the exposure-effect relationships involved. Of 142 non-vasectomized men providing semen samples, 107 had been exposed to 1,2-dibromo-3-chloropropane (DBCP) and 35 had not been exposed. There was a clearcut difference in both the distribution of sperm counts and the median counts between the exposed men and the not-exposed men, Of the exposed, 13.1% were azoospermic, 16.8% were severely oligospermic, and 15.8% were mildly oligospermic. Among the controls, 2.9% were azoospermic, none were severely oligospermic, and 5.7% were mildly oligospermic. Under workplace conditions, DBCP appears to have a selective effect on the seminiferous tubules.

Antinematodal Agents↗

PubMed1977

Infertility in male pesticide workers.

A number of cases of infertility were discovered among men working in a California pesticide factory. The suspected cause was exposure to the chemical 1,2-dibromo-3-chloropropane (D.B.C.P.). The major effects, seen in 14 of 25 non-vasectomised men, were azoospermia or oligospermia and raised serum-levels of follicle-stimulating hormone and luteinising hormone. No other major abnormalities were detected, and testosterone levels were normal. Although a quantitative estimation of exposure could not be obtained, the observed effects appeared to be related to duration of exposure to D.B.C.P.

Adult↗

PubMed1977